Zombies chase, zombies bite, zombies kill!

Renamed symbol.coffee to constant.coffee
Refactored constants out to constant.coffee
Removed extend.coffee
Refactored game state creation from Game to GameState
Refactored rendering from Game to gui.coffee
Refactored the scheduler and engine as members of Game
Modified Player to have a reference to the Game
Refactored Player.act() into a do-nothing game pause
Modified Zombie.act() to chase the player and reduce his/her health
Removed extendTest and rogueTest