Upgrading client dependancies. Upgrading to babel 6. Moving to es6 package system.

web/react/utils/constants.jsx

@@ -1,9 +1,9 @@
 // Copyright (c) 2015 Mattermost, Inc. All Rights Reserved.
 // See License.txt for license information.
 
-var keyMirror = require('keymirror');
+import keyMirror from 'keymirror';
 
-module.exports = {
+export default {
     ActionTypes: keyMirror({
         RECIEVED_ERROR: null,