Use our fork of react-gemini-scrollbar to fix resize issues

Rather than telling react-gemini-scrollbar to update every time something that
changes its size happens, try out our fork of it which uses some hackery to
listen for resizes.

src/components/structures/MessagePanel.js

@@ -159,17 +159,6 @@ module.exports = React.createClass({
         }
     },
 
-    // makes the MessagePanel update itself after it is resized (due to other
-    // changes in the DOM)
-    onResize: function() {
-        if (!this.refs.scrollPanel) { return; }
-
-        // we don't need to forceUpdate ourselves here, but we do need to
-        // forceUpdate the scrollpanel, which will make the gemini panel update
-        // itself and trigger a scroll position check.
-        this.refs.scrollPanel.forceUpdate();
-    },
-
     _getEventTiles: function() {
         var EventTile = sdk.getComponent('rooms.EventTile');