refactor($ngAnimate): simplify the animation event rewrite
refactor($ngAnimate): simplify the animation event rewrite

To avoid code duplication, use single variables for keeping
properties/events names to use. Also, fix some errors that have
happened after the rewrite from moment ago.

ggershoni/angular.js,ggershoni/angular.js,ggershoni/angular.js,ggershoni/angular.js