Properly proxy getattr within GatewayEvent (fixes #31)

disco/gateway/events.py

@@ -64,8 +64,9 @@ class GatewayEvent(six.with_metaclass(GatewayEventMeta, Model)):
         return cls(obj, client)
 
     def __getattr__(self, name):
-        if hasattr(self, '_proxy'):
-            return getattr(getattr(self, self._proxy), name)
+        _proxy = object.__getattr__(self, '_proxy', None)
+        if _proxy:
+            return getattr(_proxy, name)
         return object.__getattribute__(self, name)