Added infrastructure for basic WebSocket API (#3432)

webapp/utils/websocket_client.jsx

@@ -0,0 +1,7 @@
+// Copyright (c) 2016 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+import WebSocketClient from 'mattermost/websocket_client.jsx';
+
+var WebClient = new WebSocketClient();
+export default WebClient;