Fixes problems with SC.View's animate() refactor.  First, the original layout hash was being altered for animation before being cloned when it should have been cloned first.  This mean that if the view had not yet been rendered, it would have been rendered with the altered animate layout the first time.  Second, willRenderAnimations could be called before the animation layout was applied if the view had not yet been rendered, which would result in the animation styles being applied too early.
Fixes problem with previous invokeNext() change.  If a run loop timer is fired in the current run loop and therefore unschedule's itself, it didn't reset the internal _timeoutAt variable which meant that attempting to schedule a new run loop timer would not work.

Includes unit test.