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, 3 insertions, 10 deletions

diff --git a/src/client/gateway/prep.rs b/src/client/gateway/prep.rs
index bf4e9b3..e3b8656 100644
--- a/src/client/gateway/prep.rs
+++ b/src/client/gateway/prep.rs
@@ -17,7 +17,7 @@ use websocket::stream::WebSocketStream;
 use ::constants::{self, OpCode};
 use ::error::{Error, Result};
 use ::internal::ws_impl::{ReceiverExt, SenderExt};
-use ::model::{Event, GatewayEvent, ReadyEvent};
+use ::model::event::{Event, GatewayEvent, ReadyEvent};
 
 #[inline]
 pub fn parse_ready(event: GatewayEvent,
diff --git a/src/client/gateway/shard.rs b/src/client/gateway/shard.rs
index 61bcafc..c35fee2 100644
--- a/src/client/gateway/shard.rs
+++ b/src/client/gateway/shard.rs
@@ -16,15 +16,8 @@ use websocket::ws::sender::Sender as WsSender;
 use ::constants::OpCode;
 use ::internal::prelude::*;
 use ::internal::ws_impl::{ReceiverExt, SenderExt};
-use ::model::{
-    ChannelId,
-    Event,
-    Game,
-    GatewayEvent,
-    GuildId,
-    OnlineStatus,
-    ReadyEvent,
-};
+use ::model::event::{Event, GatewayEvent, ReadyEvent};
+use ::model::{ChannelId, Game, GuildId, OnlineStatus};
 
 #[cfg(feature="voice")]
 use ::ext::voice::Manager as VoiceManager;