Made key-ups only stop corresponding motion

Key up events were causing all motion to stop rather than just motion in
the direction corresponding to the key event. For example if you started
to press up whilst holding left, the character would go up but would
stop when you let go of left. A new motion still starts by ceasing all
previous motion.
Merge branch 'master' of https://github.com/Flowdeeps/GauntLESS