Return Integers from score and quality

I don't want them to overflow.

This required removing the QuickCheck properties because they were
taking too long. I'm not happy about that, but I don't yet know enough
about QuickCheck to fix it.
Add render function to direction
Simplify top-level spec
Make quality always positive
Refactor Game.quality
Tweak expected values

Everything should be documented, not everything should be covered. Dang
derived instances :(
Make games that are over have zero quality