ADD: added pre-existing tictactoe.py file

Created a repo for this m,n,k-game tictactoe.py script, which was
written years ago (Jan 2010). This file holds all of the game logic
, controls the GUI, and is a stand-alone script. Pygame
(http://www.pygame.org/download.shtml) is used to display the GUI.
This file is now added to the repository.
ADD: background tile image, forgot to copy over