perf(jqLite): microoptimization in chaining fn

note: no siginificant difference observed in macrobenchmarks, so this is just to make
me feel better :)

Author: IgorMinar

src/jqLite.js

@@ -930,7 +930,9 @@ forEach({
    */
   JQLite.prototype[name] = function(arg1, arg2, arg3) {
     var value;
-    for(var i=0; i < this.length; i++) {
+    var nodeCount = this.length;
+
+    for(var i=0; i < nodeCount; i++) {
       if (isUndefined(value)) {
         value = fn(this[i], arg1, arg2, arg3);
         if (isDefined(value)) {