Fix an issue where browser may be detected as touch-enabled but touch event isn't thrown.

This was causing react-grid-layout/react-grid-layout#16 (comment)

Author: STRML

lib/draggable.js

@@ -89,7 +89,7 @@ var dragEventFor = (function () {
  * get {clientX, clientY} positions of control
  * */
 function getControlPosition(e) {
-  var position = !isTouchDevice ? e : e.touches[0];
+  var position = (e.touches && e.touches[0]) || e;
   return {
     clientX: position.clientX,
     clientY: position.clientY