Added a thread class for handling the case where player 1 is a computer player. Also minor tweaks.

- if the first player was a computer player, makeComputerMoves would
have to be called in the main execution thread, causing the view to not
be updated; adding a new thread class for this solved the issue
- move setNextPlayer to after the pause in computer moves so that it
doesn't seem instantaneous if the player can't go
- removed some pointless commented out code