fix (ngAnimate): fix requestAnimationFrame for old version of Firefox

The recent $$RAFProvider which is a wrapper for the native
requestAnimationFrame method doesn't use the mozRequestAnimationFrame.
Old versions of FF (20 for example) crash if ngAnimate is included

No breaking changes and fix issue https://github.com/angular/angular.js/issues/6535

Closes #6535
Closes #6540

src/ng/raf.js

@@ -3,10 +3,12 @@
 function $$RAFProvider(){ //rAF
   this.$get = ['$window', '$timeout', function($window, $timeout) {
     var requestAnimationFrame = $window.requestAnimationFrame ||
-                                $window.webkitRequestAnimationFrame;
+                                $window.webkitRequestAnimationFrame ||
+                                $window.mozRequestAnimationFrame;
 
     var cancelAnimationFrame = $window.cancelAnimationFrame ||
-                               $window.webkitCancelAnimationFrame;
+                               $window.webkitCancelAnimationFrame ||
+                               $window.mozCancelAnimationFrame;
 
     var rafSupported = !!requestAnimationFrame;
     var raf = rafSupported