Added checking for legality of moves before playing them in the
playoutLadders() method to fix a crash. Added test to see if the player
will try to play into suicide.

Also added code and tests for a stone on the outside of a ladder being
in atari, but this is commented out as it causes a null pointer
exception as it reaches an edge of the board.
Added checking for legality of moves before playing them in the
playoutLadders() method to fix a crash. Added test to see if the player
will try to play into suicide.

Also added code and tests for a stone on the outside of a ladder being
in atari, but this is commented out as it causes a null pointer
exception as it reaches an edge of the board.