#9 Super Scrabble

[Will]

Here is my patch to implement super scrabble. Right now, there's a run-time option BOARD_SIZE in pyscrabble/constants.py that can be set at 15 or 21. I also change the way the resources/letters files are saved so letters15.txt is the regular rules and letters21.txt holds the super rules. I've been having some trouble getting it to work in 1.6.2--it's unable to load the letters definitions for some reason.

[Will]