Switch to parking_lot::{Mutex, RwLock}

Switch to the `parking_lot` crate's implementations of
`std::sync::Mutex` and `std::sync::RwLock`, which are more efficient.

A writeup on why `parking_lot` is more efficient can be read here:
<https://github.com/Amanieu/parking_lot>

Upgrade path:

Modify `mutex.lock().unwrap()` usage to `mutex.lock()` (not needing to
unwrap or handle a result), and
`rwlock.read().unwrap()`/`rwlock.write().unwrap()` usage to
`rwlock.read()` and `rwlock.write()`.

For example, modify:

```rust
use serenity::CACHE;

println!("{}", CACHE.read().unwrap().user.id);
```

to:

```rust
use serenity::CACHE;

println!("{}", CACHE.read().user.id);
```

5 files changed, 47 insertions, 50 deletions

diff --git a/src/model/guild/emoji.rs b/src/model/guild/emoji.rs
index 4a2190f..7f332ae 100644
--- a/src/model/guild/emoji.rs
+++ b/src/model/guild/emoji.rs
@@ -151,8 +151,8 @@ impl Emoji {
     /// ```
     #[cfg(feature = "cache")]
     pub fn find_guild_id(&self) -> Option<GuildId> {
-        for guild in CACHE.read().unwrap().guilds.values() {
-            let guild = guild.read().unwrap();
+        for guild in CACHE.read().guilds.values() {
+            let guild = guild.read();
 
             if guild.emojis.contains_key(&self.id) {
                 return Some(guild.id);
diff --git a/src/model/guild/guild_id.rs b/src/model/guild/guild_id.rs
index 4b9a713..efda6a8 100644
--- a/src/model/guild/guild_id.rs
+++ b/src/model/guild/guild_id.rs
@@ -305,7 +305,7 @@ impl GuildId {
 
     /// Search the cache for the guild.
     #[cfg(feature = "cache")]
-    pub fn find(&self) -> Option<Arc<RwLock<Guild>>> { CACHE.read().unwrap().guild(*self) }
+    pub fn find(&self) -> Option<Arc<RwLock<Guild>>> { CACHE.read().guild(*self) }
 
     /// Requests the guild over REST.
     ///
@@ -408,7 +408,7 @@ impl GuildId {
     /// [`utils::shard_id`]: ../utils/fn.shard_id.html
     #[cfg(all(feature = "cache", feature = "utils"))]
     #[inline]
-    pub fn shard_id(&self) -> u64 { ::utils::shard_id(self.0, CACHE.read().unwrap().shard_count) }
+    pub fn shard_id(&self) -> u64 { ::utils::shard_id(self.0, CACHE.read().shard_count) }
 
     /// Returns the Id of the shard associated with the guild.
     ///
diff --git a/src/model/guild/member.rs b/src/model/guild/member.rs
index 694de20..bca3ecb 100644
--- a/src/model/guild/member.rs
+++ b/src/model/guild/member.rs
@@ -88,7 +88,7 @@ impl Member {
             return Ok(());
         }
 
-        match http::add_member_role(self.guild_id.0, self.user.read().unwrap().id.0, role_id.0) {
+        match http::add_member_role(self.guild_id.0, self.user.read().id.0, role_id.0) {
             Ok(()) => {
                 self.roles.push(role_id);
 
@@ -111,7 +111,7 @@ impl Member {
 
         let map = EditMember::default().roles(&self.roles).0;
 
-        match http::edit_member(self.guild_id.0, self.user.read().unwrap().id.0, &map) {
+        match http::edit_member(self.guild_id.0, self.user.read().id.0, &map) {
             Ok(()) => Ok(()),
             Err(why) => {
                 self.roles.retain(|r| !role_ids.contains(r));
@@ -149,7 +149,7 @@ impl Member {
 
         http::ban_user(
             self.guild_id.0,
-            self.user.read().unwrap().id.0,
+            self.user.read().id.0,
             dmd,
             &*reason,
         )
@@ -158,9 +158,9 @@ impl Member {
     /// Determines the member's colour.
     #[cfg(all(feature = "cache", feature = "utils"))]
     pub fn colour(&self) -> Option<Colour> {
-        let cache = CACHE.read().unwrap();
+        let cache = CACHE.read();
         let guild = match cache.guilds.get(&self.guild_id) {
-            Some(guild) => guild.read().unwrap(),
+            Some(guild) => guild.read(),
             None => return None,
         };
 
@@ -187,10 +187,10 @@ impl Member {
             None => return None,
         };
 
-        let reader = guild.read().unwrap();
+        let reader = guild.read();
 
         for (cid, channel) in &reader.channels {
-            if reader.permissions_for(*cid, self.user.read().unwrap().id).read_messages() {
+            if reader.permissions_for(*cid, self.user.read().id).read_messages() {
                 return Some(channel.clone());
             }
         }
@@ -206,7 +206,7 @@ impl Member {
         self.nick
             .as_ref()
             .map(Cow::Borrowed)
-            .unwrap_or_else(|| Cow::Owned(self.user.read().unwrap().name.clone()))
+            .unwrap_or_else(|| Cow::Owned(self.user.read().name.clone()))
     }
 
     /// Returns the DiscordTag of a Member, taking possible nickname into account.
@@ -215,7 +215,7 @@ impl Member {
         format!(
             "{}#{}",
             self.display_name(),
-            self.user.read().unwrap().discriminator
+            self.user.read().discriminator
         )
     }
 
@@ -231,7 +231,7 @@ impl Member {
     pub fn edit<F: FnOnce(EditMember) -> EditMember>(&self, f: F) -> Result<()> {
         let map = f(EditMember::default()).0;
 
-        http::edit_member(self.guild_id.0, self.user.read().unwrap().id.0, &map)
+        http::edit_member(self.guild_id.0, self.user.read().id.0, &map)
     }
 
     /// Kick the member from the guild.
@@ -274,17 +274,16 @@ impl Member {
 
             let has_perms = CACHE
                 .read()
-                .unwrap()
                 .guilds
                 .get(&self.guild_id)
-                .map(|guild| guild.read().unwrap().has_perms(req));
+                .map(|guild| guild.read().has_perms(req));
 
             if let Some(Ok(false)) = has_perms {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
             }
         }
 
-        self.guild_id.kick(self.user.read().unwrap().id)
+        self.guild_id.kick(self.user.read().id)
     }
 
     /// Returns the permissions for the member.
@@ -314,18 +313,18 @@ impl Member {
             None => return Err(From::from(ModelError::GuildNotFound)),
         };
 
-        let guild = guild.read().unwrap();
+        let guild = guild.read();
 
-        let default_channel = match guild.default_channel(self.user.read().unwrap().id) {
+        let default_channel = match guild.default_channel(self.user.read().id) {
             Some(dc) => dc,
             None => return Err(From::from(ModelError::ItemMissing)),
         };
 
-        let default_channel_reader = default_channel.read().unwrap();
+        let default_channel_reader = default_channel.read();
 
         Ok(
             guild
-                .permissions_for(default_channel_reader.id, self.user.read().unwrap().id),
+                .permissions_for(default_channel_reader.id, self.user.read().id),
         )
     }
 
@@ -344,7 +343,7 @@ impl Member {
             return Ok(());
         }
 
-        match http::remove_member_role(self.guild_id.0, self.user.read().unwrap().id.0, role_id.0) {
+        match http::remove_member_role(self.guild_id.0, self.user.read().id.0, role_id.0) {
             Ok(()) => {
                 self.roles.retain(|r| r.0 != role_id.0);
 
@@ -366,7 +365,7 @@ impl Member {
 
         let map = EditMember::default().roles(&self.roles).0;
 
-        match http::edit_member(self.guild_id.0, self.user.read().unwrap().id.0, &map) {
+        match http::edit_member(self.guild_id.0, self.user.read().id.0, &map) {
             Ok(()) => Ok(()),
             Err(why) => {
                 self.roles.extend_from_slice(role_ids);
@@ -385,19 +384,17 @@ impl Member {
     pub fn roles(&self) -> Option<Vec<Role>> {
         CACHE
             .read()
-            .unwrap()
             .guilds
             .values()
             .find(|guild| {
-                guild.read().unwrap().members.values().any(|m| {
-                    m.user.read().unwrap().id == self.user.read().unwrap().id &&
+                guild.read().members.values().any(|m| {
+                    m.user.read().id == self.user.read().id &&
                     m.joined_at == self.joined_at
                 })
             })
             .map(|guild| {
                 guild
                     .read()
-                    .unwrap()
                     .roles
                     .values()
                     .filter(|role| self.roles.contains(&role.id))
@@ -420,7 +417,7 @@ impl Member {
     /// [Ban Members]: permissions/constant.BAN_MEMBERS.html
     #[cfg(feature = "cache")]
     pub fn unban(&self) -> Result<()> {
-        http::remove_ban(self.guild_id.0, self.user.read().unwrap().id.0)
+        http::remove_ban(self.guild_id.0, self.user.read().id.0)
     }
 }
 
@@ -436,6 +433,6 @@ impl Display for Member {
     ///
     // This is in the format of `<@USER_ID>`.
     fn fmt(&self, f: &mut Formatter) -> FmtResult {
-        Display::fmt(&self.user.read().unwrap().mention(), f)
+        Display::fmt(&self.user.read().mention(), f)
     }
 }
diff --git a/src/model/guild/mod.rs b/src/model/guild/mod.rs
index 73dfa73..ea6cb17 100644
--- a/src/model/guild/mod.rs
+++ b/src/model/guild/mod.rs
@@ -155,17 +155,17 @@ impl Guild {
 
     #[cfg(feature = "cache")]
     fn has_perms(&self, mut permissions: Permissions) -> Result<bool> {
-        let member = match self.members.get(&CACHE.read().unwrap().user.id) {
+        let member = match self.members.get(&CACHE.read().user.id) {
             Some(member) => member,
             None => return Err(Error::Model(ModelError::ItemMissing)),
         };
 
-        let default_channel = match self.default_channel(member.user.read().unwrap().id) {
+        let default_channel = match self.default_channel(member.user.read().id) {
             Some(dc) => dc,
             None => return Err(Error::Model(ModelError::ItemMissing)),
         };
 
-        let perms = self.permissions_for(default_channel.read().unwrap().id, member.user.read().unwrap().id);
+        let perms = self.permissions_for(default_channel.read().id, member.user.read().id);
         permissions.remove(perms);
 
         Ok(permissions.is_empty())
@@ -406,7 +406,7 @@ impl Guild {
     pub fn delete(&self) -> Result<PartialGuild> {
         #[cfg(feature = "cache")]
         {
-            if self.owner_id != CACHE.read().unwrap().user.id {
+            if self.owner_id != CACHE.read().user.id {
                 let req = Permissions::MANAGE_GUILD;
 
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -723,9 +723,9 @@ impl Guild {
         self.members
             .values()
             .find(|member| {
-                let name_matches = member.user.read().unwrap().name == name;
+                let name_matches = member.user.read().name == name;
                 let discrim_matches = match discrim {
-                    Some(discrim) => member.user.read().unwrap().discriminator == discrim,
+                    Some(discrim) => member.user.read().discriminator == discrim,
                     None => true,
                 };
 
@@ -744,7 +744,7 @@ impl Guild {
     /// - "zey", "zeyla", "zey mei"
     /// If 'case_sensitive' is false, the following are not found:
     /// - "Zey", "ZEYla", "zeY mei"
-    /// 
+    ///
     /// [`Member`]: struct.Member.html
     pub fn members_starting_with(&self, prefix: &str, case_sensitive: bool) -> Vec<&Member> {
         self.members
@@ -752,11 +752,11 @@ impl Guild {
             .filter(|member|
 
                 if case_sensitive {
-                    member.user.read().unwrap().name.starts_with(prefix)
+                    member.user.read().name.starts_with(prefix)
                 } else {
-                    starts_with_case_insensitive(&member.user.read().unwrap().name, &prefix)
+                    starts_with_case_insensitive(&member.user.read().name, &prefix)
                 }
-                
+
                 || member.nick.as_ref()
                     .map_or(false, |nick|
 
@@ -773,7 +773,7 @@ impl Guild {
     /// - "zeyla", "meiyla", "yladenisyla"
     /// If 'case_sensitive' is false, the following are not found:
     /// - "zeYLa", "meiyLa", "LYAdenislyA"
-    /// 
+    ///
     /// [`Member`]: struct.Member.html
     pub fn members_containing(&self, substring: &str, case_sensitive: bool) -> Vec<&Member> {
         self.members
@@ -781,11 +781,11 @@ impl Guild {
             .filter(|member|
 
                 if case_sensitive {
-                    member.user.read().unwrap().name.contains(substring)
+                    member.user.read().name.contains(substring)
                 } else {
-                    contains_case_insensitive(&member.user.read().unwrap().name, &substring)
+                    contains_case_insensitive(&member.user.read().name, &substring)
                 }
-                
+
                 || member.nick.as_ref()
                     .map_or(false, |nick|
 
@@ -849,7 +849,7 @@ impl Guild {
             } else {
                 warn!(
                     "(╯°□°）╯︵ ┻━┻ {} on {} has non-existent role {:?}",
-                    member.user.read().unwrap().id,
+                    member.user.read().id,
                     self.id,
                     role
                 );
@@ -862,7 +862,7 @@ impl Guild {
         }
 
         if let Some(channel) = self.channels.get(&channel_id) {
-            let channel = channel.read().unwrap();
+            let channel = channel.read();
 
             // If this is a text channel, then throw out voice permissions.
             if channel.kind == ChannelType::Text {
@@ -1102,7 +1102,7 @@ impl Guild {
     /// impl EventHandler for Handler {
     ///     fn on_message(&self, _: Context, msg: Message) {
     ///         if let Some(arc) = msg.guild_id().unwrap().find() {
-    ///             if let Some(role) = arc.read().unwrap().role_by_name("role_name") {
+    ///             if let Some(role) = arc.read().role_by_name("role_name") {
     ///                 println!("{:?}", role);
     ///             }
     ///         }
diff --git a/src/model/guild/role.rs b/src/model/guild/role.rs
index 7ac7019..3ed718e 100644
--- a/src/model/guild/role.rs
+++ b/src/model/guild/role.rs
@@ -106,8 +106,8 @@ impl Role {
     /// [`ModelError::GuildNotFound`]: enum.ModelError.html#variant.GuildNotFound
     #[cfg(feature = "cache")]
     pub fn find_guild(&self) -> Result<GuildId> {
-        for guild in CACHE.read().unwrap().guilds.values() {
-            let guild = guild.read().unwrap();
+        for guild in CACHE.read().guilds.values() {
+            let guild = guild.read();
 
             if guild.roles.contains_key(&RoleId(self.id.0)) {
                 return Ok(guild.id);
@@ -168,10 +168,10 @@ impl RoleId {
     /// Search the cache for the role.
     #[cfg(feature = "cache")]
     pub fn find(&self) -> Option<Role> {
-        let cache = CACHE.read().unwrap();
+        let cache = CACHE.read();
 
         for guild in cache.guilds.values() {
-            let guild = guild.read().unwrap();
+            let guild = guild.read();
 
             if !guild.roles.contains_key(self) {
                 continue;