Move events into their own module

The events were cluttering the `model` module, and so are now moved into
their own `model::event` module.

As users should not usually have to work with events all that much -
only currently in some rarely used event handlers - this change should
not be much more effort to import from.

i.e.:

```rs
use serenity::model::event::ChannelPinsAckEvent;
```
vs. the now-old:

```rs
use serenity::model::ChannelPinsAckEvent;
```

2 files changed, 2 insertions, 1 deletions

diff --git a/src/ext/cache/mod.rs b/src/ext/cache/mod.rs
index 28a8a6c..7c4d3a5 100644
--- a/src/ext/cache/mod.rs
+++ b/src/ext/cache/mod.rs
@@ -3,6 +3,7 @@ use std::collections::HashMap;
 use std::default::Default;
 use std::mem;
 use ::model::*;
+use ::model::event::*;
 
 /// A cache of all events received over a [`Connection`], where storing at least
 /// some data from the event is possible.
diff --git a/src/ext/framework/mod.rs b/src/ext/framework/mod.rs
index 8c807dc..39f2148 100644
--- a/src/ext/framework/mod.rs
+++ b/src/ext/framework/mod.rs
@@ -82,7 +82,7 @@ pub struct Framework {
     /// itself.
     ///
     /// [`Client::on_message`]: ../../client/struct.Client.html#method.on_message
-    /// [`Event::MessageCreate`]: ../../model/enum.Event.html#variant.MessageCreate
+    /// [`Event::MessageCreate`]: ../../model/event/enum.Event.html#variant.MessageCreate
     pub initialized: bool,
 }