Notify websockets with the new user list when someone logs in

Signed-off-by: Romain Gauthier <romain.gauthier@monkeypatch.me>
Signed-off-by: Dan Mosedale <dmose@meer.net>
Signed-off-by: Nicolas Perriault <nperriault@gmail.com>
Add a shutdown method to the app
Remove the websocket drop test
Replace a map by a forEach.
Merge pull request #23 from tOkeshu/join-notification

Notify websockets with the new user list when someone logs in