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, 1 insertions, 1 deletions

diff --git a/src/model/channel/reaction.rs b/src/model/channel/reaction.rs
index 8edc2e9..1a40ecb 100644
--- a/src/model/channel/reaction.rs
+++ b/src/model/channel/reaction.rs
@@ -48,7 +48,7 @@ impl Reaction {
     pub fn delete(&self) -> Result<()> {
         let user_id = feature_cache! {
             {
-                let user = if self.user_id == CACHE.read().unwrap().user.id {
+                let user = if self.user_id == CACHE.read().user.id {
                     None
                 } else {
                     Some(self.user_id.0)