Tic-Tac-Toe - simple console version

This is basically just a simple console version of Tic-Tac-Toe with an AI that's able to win the game as long as it goes first and the player doesn't play the center square. It also has comprehensive code coverage and passes pep8/pylint.

Code coverage: 100% lines, 100% branches
PEP8: 0 errors (--max-line-length=110)
pylint: 0 errors