Realized whene Tween\finish is called

* finish is called from Tweener\upadetTweens. Unfortunately, finish is
  file (Tween.moon) local and wouldn't have been callable. I've fixed
  that and removed the UPDATE EventListener.
* Found an issue when Tween\update could still be called on non-active
  tweens. I believe this is an issue not a feature.
Update Tween tests for previous commit

* Subclass Tween to make update behave like Tweener\updateTweens
Add Tween test for cancel
Added Tween test for complete callback