Correction to Game model and tests

There is a bit of code missing in the Game initialization method... if board data is present, it will be overwritten by a blank board.  This causes the #check_for_winner test to fail even when the check_for_winner method is correct.

Also, the game tests have a small typo - :blue should be a string, not a symbol, so that it can be compared to the string stored in the game object.