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/examples/05_command_framework/src/main.rs b/examples/05_command_framework/src/main.rs
index 437c44e..975e216 100644
--- a/examples/05_command_framework/src/main.rs
+++ b/examples/05_command_framework/src/main.rs
@@ -199,7 +199,7 @@ command!(about_role(_ctx, msg, args) {
     if let Some(guild) = msg.guild() {
         // `role_by_name()` allows us to attempt attaining a reference to a role
         // via its name.
-        if let Some(role) = guild.read().unwrap().role_by_name(&potential_role_name) {
+        if let Some(role) = guild.read().role_by_name(&potential_role_name) {
             if let Err(why) = msg.channel_id.say(&format!("Role-ID: {}", role.id)) {
                 println!("Error sending message: {:?}", why);
             }