PLT-4343 Fixes for mobile main menu (#4148)

* Fixed mobile app link in the main menu to be displayed on mobile browsers

* Fixed doubled up dividers in mobile menu

* Added scrolling to mobile main menu

webapp/components/create_post.jsx

@@ -199,7 +199,7 @@ export default class CreatePost extends React.Component {
     }
 
     postMsgKeyPress(e) {
-        if (!UserAgent.isMobileApp() && ((this.state.ctrlSend && e.ctrlKey) || !this.state.ctrlSend)) {
+        if (!UserAgent.isMobile() && ((this.state.ctrlSend && e.ctrlKey) || !this.state.ctrlSend)) {
             if (e.which === KeyCodes.ENTER && !e.shiftKey && !e.altKey) {
                 e.preventDefault();
                 ReactDOM.findDOMNode(this.refs.textbox).blur();