Fixed zombie disco dancing on roam

And stopped them from jumping while falling.

Kevin:
- at edge reset moveRightUntilHit but was AFTER the movement, i put it
before
- at edge move his position, but this was after stopMovement set vel to
0 for roaming.  The fix was to stop stopMovement from setting vel to 0
and to make moveRight/Left set the velocity instead of adding it.