Stub emptyFunction (no need for require) and remove unused classSet import.

Author: STRML

lib/draggable.js

@@ -2,8 +2,7 @@
 
 /** @jsx React.DOM */
 var React = require('react');
-var emptyFunction = require('react/lib/emptyFunction');
-var CX = React.addons.classSet;
+var emptyFunction = function(){};
 
 function createUIEvent(draggable) {
 	return {