Docs: Move to new intra-doc links, make events non-exhaustive. (#19)

Far cleaner and more reliable than the old doc-link pattern. Also allowed me to spot some event types and sources which should have been made non_exhaustive.

src/serenity.rs

@@ -13,7 +13,7 @@ use std::sync::Arc;
 /// Zero-size type used to retrieve the registered [`Songbird`] instance
 /// from serenity's inner TypeMap.
 ///
-/// [`Songbird`]: ../struct.Songbird.html
+/// [`Songbird`]: Songbird
 pub struct SongbirdKey;
 
 impl TypeMapKey for SongbirdKey {
@@ -54,7 +54,7 @@ pub trait SerenityInit {
     /// Registers a new Songbird voice system with serenity, storing it for easy
     /// access via [`get`].
     ///
-    /// [`get`]: fn.get.html
+    /// [`get`]: get
     fn register_songbird(self) -> Self;
     /// Registers a given Songbird voice system with serenity, as above.
     fn register_songbird_with(self, voice: Arc<Songbird>) -> Self;