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);
```

1 files changed, 5 insertions, 5 deletions

diff --git a/src/builder/create_embed.rs b/src/builder/create_embed.rs
index a6b264c..f7dc0b1 100644
--- a/src/builder/create_embed.rs
+++ b/src/builder/create_embed.rs
@@ -249,20 +249,20 @@ impl CreateEmbed {
     /// impl EventHandler for Handler {
     ///     fn on_guild_member_addition(&self, _: Context, guild_id: GuildId, member: Member) {
     ///         use serenity::client::CACHE;
-    ///         let cache = CACHE.read().unwrap();
+    ///         let cache = CACHE.read();
     ///
     ///         if let Some(guild) = cache.guild(guild_id) {
-    ///             let guild = guild.read().unwrap();
+    ///             let guild = guild.read();
     ///
     ///             let channel_search = guild
     ///                 .channels
     ///                 .values()
-    ///                 .find(|c| c.read().unwrap().name == "join-log");
+    ///                 .find(|c| c.read().name == "join-log");
     ///
     ///             if let Some(channel) = channel_search {
-    ///                 let user = member.user.read().unwrap();
+    ///                 let user = member.user.read();
     ///
-    ///                 let _ = channel.read().unwrap().send_message(|m| m
+    ///                 let _ = channel.read().send_message(|m| m
     ///                     .embed(|e| {
     ///                         let mut e = e
     ///                             .author(|a| a.icon_url(&user.face()).name(&user.name))