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/TimelinePanel.js

@@ -508,13 +508,6 @@ var TimelinePanel = React.createClass({
         return null;
     },
 
-    // makes the TimelinePanel update itself after it is resized (due to other
-    // changes in the DOM)
-    onResize: function() {
-        if (!this.refs.messagePanel) { return; }
-        this.refs.messagePanel.onResize();
-    },
-
     _initTimeline: function(props) {
         var initialEvent = props.eventId;
         var pixelOffset = props.eventPixelOffset;