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, 6 insertions, 6 deletions

diff --git a/src/model/channel/channel_id.rs b/src/model/channel/channel_id.rs
index f728191..4034fb9 100644
--- a/src/model/channel/channel_id.rs
+++ b/src/model/channel/channel_id.rs
@@ -224,14 +224,14 @@ impl ChannelId {
 
     /// Search the cache for the channel with the Id.
     #[cfg(feature = "cache")]
-    pub fn find(&self) -> Option<Channel> { CACHE.read().unwrap().channel(*self) }
+    pub fn find(&self) -> Option<Channel> { CACHE.read().channel(*self) }
 
     /// Search the cache for the channel. If it can't be found, the channel is
     /// requested over REST.
     pub fn get(&self) -> Result<Channel> {
         #[cfg(feature = "cache")]
         {
-            if let Some(channel) = CACHE.read().unwrap().channel(*self) {
+            if let Some(channel) = CACHE.read().channel(*self) {
                 return Ok(channel);
             }
         }
@@ -311,13 +311,13 @@ impl ChannelId {
         };
 
         Some(match channel {
-            Guild(channel) => channel.read().unwrap().name().to_string(),
-            Group(channel) => match channel.read().unwrap().name() {
+            Guild(channel) => channel.read().name().to_string(),
+            Group(channel) => match channel.read().name() {
                 Cow::Borrowed(name) => name.to_string(),
                 Cow::Owned(name) => name,
             },
-            Category(category) => category.read().unwrap().name().to_string(),
-            Private(channel) => channel.read().unwrap().name(),
+            Category(category) => category.read().name().to_string(),
+            Private(channel) => channel.read().name(),
         })
     }