Adding the first version of the TicTacToe class
Small refactoring on TicTacToe test

Extracted some code which is going to be used in all test cases
TicTacToe now can handle a full turn and both Player and Ai will move
TicTacToe can tell when a player wins
TicTacToe::checkForWinners() will return false if nobody won
Refactoring TicTacToe, removing duplication
Players can now draw