Update bitflags, other dependencies

Bitflags changed its macro codegen from creating constants to associated
constants on structs.

Upgrade path:

Update code from:

```rust
use serenity::model::permissions::{ADD_REACTIONS, MANAGE_MESSAGES};

foo(vec![ADD_REACTIONS, MANAGE_MESSAGES]);
```

to:

```rust
use serenity::model::Permissions;

foo(vec![Permissions::ADD_REACTIONS, Permissions::MANAGE_MESSAGES]);
```

4 files changed, 21 insertions, 21 deletions

diff --git a/src/model/channel/channel_category.rs b/src/model/channel/channel_category.rs
index c88f7fa..50df35e 100644
--- a/src/model/channel/channel_category.rs
+++ b/src/model/channel/channel_category.rs
@@ -60,7 +60,7 @@ impl ChannelCategory {
     pub fn delete(&self) -> Result<()> {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::MANAGE_CHANNELS;
+            let req = Permissions::MANAGE_CHANNELS;
 
             if !utils::user_has_perms(self.id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -86,7 +86,7 @@ impl ChannelCategory {
         where F: FnOnce(EditChannel) -> EditChannel {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::MANAGE_CHANNELS;
+            let req = Permissions::MANAGE_CHANNELS;
 
             if !utils::user_has_perms(self.id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
diff --git a/src/model/channel/guild_channel.rs b/src/model/channel/guild_channel.rs
index 20e5d41..a6bc597 100644
--- a/src/model/channel/guild_channel.rs
+++ b/src/model/channel/guild_channel.rs
@@ -109,7 +109,7 @@ impl GuildChannel {
         where F: FnOnce(CreateInvite) -> CreateInvite {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::CREATE_INVITE;
+            let req = Permissions::CREATE_INVITE;
 
             if !utils::user_has_perms(self.id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -135,7 +135,7 @@ impl GuildChannel {
     /// permissions:
     ///
     /// ```rust,no_run
-    /// # use serenity::model::{ChannelId, UserId};
+    /// # use serenity::model::{ChannelId, Permissions, UserId};
     /// # use std::error::Error;
     /// #
     /// # fn try_main() -> Result<(), Box<Error>> {
@@ -149,8 +149,8 @@ impl GuildChannel {
     /// };
     /// use serenity::CACHE;
     ///
-    /// let allow = permissions::SEND_MESSAGES;
-    /// let deny = permissions::SEND_TTS_MESSAGES | permissions::ATTACH_FILES;
+    /// let allow = Permissions::SEND_MESSAGES;
+    /// let deny = Permissions::SEND_TTS_MESSAGES | Permissions::ATTACH_FILES;
     /// let overwrite = PermissionOverwrite {
     ///     allow: allow,
     ///     deny: deny,
@@ -177,7 +177,7 @@ impl GuildChannel {
     /// permissions:
     ///
     /// ```rust,no_run
-    /// # use serenity::model::{ChannelId, UserId};
+    /// # use serenity::model::{ChannelId, Permissions, UserId};
     /// # use std::error::Error;
     /// #
     /// # fn try_main() -> Result<(), Box<Error>> {
@@ -191,8 +191,8 @@ impl GuildChannel {
     /// };
     /// use serenity::CACHE;
     ///
-    /// let allow = permissions::SEND_MESSAGES;
-    /// let deny = permissions::SEND_TTS_MESSAGES | permissions::ATTACH_FILES;
+    /// let allow = Permissions::SEND_MESSAGES;
+    /// let deny = Permissions::SEND_TTS_MESSAGES | Permissions::ATTACH_FILES;
     /// let overwrite = PermissionOverwrite {
     ///     allow: allow,
     ///     deny: deny,
@@ -233,7 +233,7 @@ impl GuildChannel {
     pub fn delete(&self) -> Result<Channel> {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::MANAGE_CHANNELS;
+            let req = Permissions::MANAGE_CHANNELS;
 
             if !utils::user_has_perms(self.id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -305,7 +305,7 @@ impl GuildChannel {
         where F: FnOnce(EditChannel) -> EditChannel {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::MANAGE_CHANNELS;
+            let req = Permissions::MANAGE_CHANNELS;
 
             if !utils::user_has_perms(self.id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -473,8 +473,8 @@ impl GuildChannel {
     /// let permissions =
     /// channel.read().unwrap().permissions_for(current_user_id).unwrap();
     ///
-    /// if !permissions.contains(permissions::ATTACH_FILES |
-    /// permissions::SEND_MESSAGES) {
+    /// if !permissions.contains(Permissions::ATTACH_FILES |
+    /// Permissions::SEND_MESSAGES) {
     ///             return;
     ///         }
     ///
@@ -605,7 +605,7 @@ impl GuildChannel {
     pub fn send_message<F: FnOnce(CreateMessage) -> CreateMessage>(&self, f: F) -> Result<Message> {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::SEND_MESSAGES;
+            let req = Permissions::SEND_MESSAGES;
 
             if !utils::user_has_perms(self.id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
diff --git a/src/model/channel/message.rs b/src/model/channel/message.rs
index d36d290..7b94540 100644
--- a/src/model/channel/message.rs
+++ b/src/model/channel/message.rs
@@ -137,7 +137,7 @@ impl Message {
     pub fn delete(&self) -> Result<()> {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::MANAGE_MESSAGES;
+            let req = Permissions::MANAGE_MESSAGES;
             let is_author = self.author.id == CACHE.read().unwrap().user.id;
             let has_perms = utils::user_has_perms(self.channel_id, req)?;
 
@@ -165,7 +165,7 @@ impl Message {
     pub fn delete_reactions(&self) -> Result<()> {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::MANAGE_MESSAGES;
+            let req = Permissions::MANAGE_MESSAGES;
 
             if !utils::user_has_perms(self.channel_id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -394,7 +394,7 @@ impl Message {
     pub fn pin(&self) -> Result<()> {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::MANAGE_MESSAGES;
+            let req = Permissions::MANAGE_MESSAGES;
 
             if !utils::user_has_perms(self.channel_id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -421,7 +421,7 @@ impl Message {
     pub fn react<R: Into<ReactionType>>(&self, reaction_type: R) -> Result<()> {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::ADD_REACTIONS;
+            let req = Permissions::ADD_REACTIONS;
 
             if !utils::user_has_perms(self.channel_id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -460,7 +460,7 @@ impl Message {
 
         #[cfg(feature = "cache")]
         {
-            let req = permissions::SEND_MESSAGES;
+            let req = Permissions::SEND_MESSAGES;
 
             if !utils::user_has_perms(self.channel_id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -494,7 +494,7 @@ impl Message {
     pub fn unpin(&self) -> Result<()> {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::MANAGE_MESSAGES;
+            let req = Permissions::MANAGE_MESSAGES;
 
             if !utils::user_has_perms(self.channel_id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
diff --git a/src/model/channel/reaction.rs b/src/model/channel/reaction.rs
index 605ac7f..2420ba7 100644
--- a/src/model/channel/reaction.rs
+++ b/src/model/channel/reaction.rs
@@ -61,7 +61,7 @@ impl Reaction {
                 //
                 // * The `Manage Messages` permission.
                 if user.is_some() {
-                    let req = permissions::MANAGE_MESSAGES;
+                    let req = Permissions::MANAGE_MESSAGES;
 
                     if !utils::user_has_perms(self.channel_id, req).unwrap_or(true) {
                         return Err(Error::Model(ModelError::InvalidPermissions(req)));