Working on Jump animation

- this.isFalling never created in the Mario constructor. Added this in
the constructor
- Added the max ARC height of the JUMP animation. Once this is touched,
mario will start falling
- Implement checks in the listener so more keypresses will not interfer
with the jumping/falling animations
- Started to implement the Running/Walking JUMP (incomplete)
- Created a floor value, so mario always know where the floor is. This
is the Y value that mario is started at in the Level creation.