Convert CommonJS exports to ES6-compatible exports

We use `export default` begrudgingly here. Ideally we'd use just `export`, though this entire SDK expects things to be exported as a default. Instead of breaking everything, we'll sacrifice our export pattern for a smaller diff - a later commit can always do the default export -> regular export conversion.

src/components/views/rooms/PinnedEventTile.js

@@ -25,7 +25,7 @@ import MemberAvatar from "../avatars/MemberAvatar";
 import { _t } from '../../../languageHandler';
 import {formatFullDate} from '../../../DateUtils';
 
-module.exports = createReactClass({
+export default createReactClass({
     displayName: 'PinnedEventTile',
     propTypes: {
         mxRoom: PropTypes.object.isRequired,