Merge pull request #14 from jcbrock/ImprovingAI

Major improvements to AI - added row weight helped a ton
Merge branch 'ImprovingAI' of github.com:jcbrock/UnityTetris
Reworked AI to make more sense and much more readable. Now I need to figure out how to trigger AI to run
Changed scene rules to publish out various updates (new shape, game ended) that higher classes can subscribe to. SceneRules is okay with this, beacuse it doesn't have any knowledge of who is subscribing to it, it is just pushing information out there