VoiceConnection rework (#1183)

* VoiceConnection rework

- improves codebase
- removes concept of pending connections
- attempts to fix memory leaks by removing EventEmitter listeners
- makes voice connections keep track of its own channel when it is moved by another user
- allows voice connections to reconnect when Discord falls back to another voice server or a region change occurs
- adds events for some of the aforementioned events

* Removed unused code

* More clean up / bugfixes

* Added typedefs to Status and VoiceStatus constants

src/client/voice/VoiceUDPClient.js

@@ -47,12 +47,12 @@ class VoiceConnectionUDPClient extends EventEmitter {
 
   shutdown() {
     if (this.socket) {
+      this.socket.removeAllListeners('message');
       try {
         this.socket.close();
-      } catch (e) {
-        return;
+      } finally {
+        this.socket = null;
       }
-      this.socket = null;
     }
   }