Remove tests of UINavigationControllerDelegate and introduce an assertion handler.
Refactors UINavigationController+Spec to pass through to the internal push/pop methods without animation

No more advancing the run loop
iOS 8.1 wants UINavigationController tests to happen inside a window, otherwise "unbalanced calls to begin/end transitions" will emit
iOS 8.1 has a bug in 64 bit simulator where some internal assertions don't happen, and therefore some specs will fail on that runtime (http://openradar.appspot.com/18831038)
Fixes a subtle bug which required compilation with ARC disabled
Also cleans up the assertion handler test in UICollectionViewCell+Spec