perf(jqLite): optimize off()

'for in' is much faster than Object.keys() and since the events object is ours, we know
that we don't need to worry about prototypically inherited properties so we can skip
expensive hasOwnProperty check.

http://jsperf.com/for-in-vs-object-keys2

Author: IgorMinar

src/jqLite.js

@@ -270,16 +270,11 @@ function jqLiteOff(element, type, fn, unsupported) {
   var expandoStore = jqLiteExpandoStore(element);
   var events = expandoStore && expandoStore.events;
   var handle = expandoStore && expandoStore.handle;
-  var i;
-  var types;
 
   if (!handle) return; //no listeners registered
 
-  if (isUndefined(type)) {
-    types = Object.keys(events);
-    i = types.length;
-    while (i--) {
-      type = types[i];
+  if (!type) {
+    for (type in events) {
       if (type !== '$destroy') {
         removeEventListenerFn(element, type, events[type]);
       }