Apply animation on ui-view instead of contents.

AngularJS 1.2 animation $animate.enter(element, parent, after, done)
method applies the animation classes to element and not parent. To
achieve the desired result this commit injects an anchor comment element
to animate ui-view and its contents beside the anchor element.

This enables you to apply your animation class directly on the ui-view
element instead of wrapping your templates for animation to work. See
#320.