Migrate away from React.createClass for non-auth structures. React 16 :D

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

src/components/structures/MatrixChat.js

@@ -20,6 +20,7 @@ limitations under the License.
 import Promise from 'bluebird';
 
 import React from 'react';
+import createReactClass from 'create-react-class';
 import PropTypes from 'prop-types';
 import Matrix from "matrix-js-sdk";
 
@@ -106,7 +107,7 @@ const ONBOARDING_FLOW_STARTERS = [
     'view_create_group',
 ];
 
-export default React.createClass({
+export default createReactClass({
     // we export this so that the integration tests can use it :-S
     statics: {
         VIEWS: VIEWS,