feat(transition): emulateTransitionEnd implementation (BLOCKS #934)

TWBS uses this fallback path to provide functional behaviour on browsers which will not use a transition.

I have found that this sort of behaviour is required particularly for Firefox releases prior to version 16,
because Bootstrap's stock CSS does not provide -moz-prefixed transition properties, and prefixless transition
is not supported until FF16.

Using this emulateTransitionEnd functionality, we can have functional behaviour on browsers which do not
support transitions, even though we do detect that we support transitionend events. This can prevent a lot of
buggy behaviour.

I'd like to provide automated tests for this functionality, and am working on that now.