Real-time Chat (#7664)

* feat(realtime-chat): add Pusher library to the server

* feat(realtime-chat): only for private groups

* feat(realtime-chat): add authentication endpoint for Pusher

* feat(realtime-chat): client proof of concept

* fix typo in apidoc

* feat(realtime-chat): redo authentication and write integration tests

* remove firebase code

* fix client side tests

* fix line ending in bower.json

* feat(realtime chat): use presence channels for parties, send events & disconnect clients if user leaves or is removed from party, automatically update UI

* pusher: enable all events in the background

* fix pusher integration tests

website/server/controllers/api-v3/user.js

@@ -13,7 +13,6 @@ import {
 import { model as User } from '../../models/user';
 import Bluebird from 'bluebird';
 import _ from 'lodash';
-import * as firebase from '../../libs/api-v3/firebase';
 import * as passwordUtils from '../../libs/api-v3/password';
 
 let api = {};
@@ -230,8 +229,6 @@ api.deleteUser = {
     await user.remove();
 
     res.respond(200, {});
-
-    firebase.deleteUser(user._id);
   },
 };