perf(ngClass): improve even-odd checking

This now uses the same technique as ngRepeat.

Author: marijaselakovic

src/ng/directive/ngClass.js

@@ -69,7 +69,9 @@ function classDirective(name, selector) {
         }
 
         function ngClassWatchAction(newVal) {
-          if (selector === true || scope.$index % 2 === selector) {
+          // jshint bitwise: false
+          if (selector === true || (scope.$index & 1) === selector) {
+          // jshint bitwise: true
             var newClasses = arrayClasses(newVal || []);
             if (!oldVal) {
               addClasses(newClasses);