Minimum viable scoring engine.

The goal of this PR Is to end up with something we can actually use to score a game of snooker.

It doesn't handle fouls automatically, so relies on the honesty of players, LOL. 

It also doesn't yet undo, nor does it track and show individual breaks yet... that's all coming soon.

![smaller](https://cloud.githubusercontent.com/assets/22635/5057259/4edaca82-6d09-11e4-9200-c5a9b27502e2.gif)