Made event handlers Disposable.

- Next step is to write tests and then utilize the dispose ability throughout the internal classes.

#42
Made the ImageSource Disposable.

#46
Modified other disposable objects to dispose of their events.

#42
Made the keyboard handler disposable, this involved tracking the dom bound events so that they could then be unbound.

#47
Added unit tests to verify KeyboardHandler's dispose functionality.

#47
Made the MouseHandler disposable.

- This involved tracking all dom bound events so that they could then be unbound on dispose.

#48
Added tests to verify MouseHandler's dispose functionality.

#48
Made the InputManager disposable.

- Essentially just disposes the MouseHandler and KeyboardHandler.
- Added the dispose event to the game's dispose.

#49
Added InputManager tests to verify it's dispose functionality.

#49
Made SpriteAnimation disposable.

- It tracks an onComplete event so it needed to be disposable in order to untrack data.

#51
Added a test to verify that SpriteAnimation's dispose unbinds all events.

#51
Made AudioClip disposable.

- Can only dispose audio clips once because they null out their audio pieces.

#52
Added tests to verify that AudioClip's dispose function works correctly.

#51
Made the tween class disposable.  This is to unbind all events to ensure that no more data is tracked.

#53
Added a tween test to verify that tweens dispose works as expected