AI Spec:  Added blocks a win for opposing player.
AI Spec: Added takes a win for itself.
AI Spec:  Ensure we take a win before we take a block.
Refactor:  Extract discover_enemy_token().
AI Spec:  Evaluate board returns 1 for a game the AI wins.
AI Spec:  evaluate_board returns -1 if the AI loses the board.
AI Spec: evaluate_board() returns 0 for a draw game.
AI Spec:  evaluate_board returns nil for games in progress
Refactor a bit to use evaulate_board()
Factor out a method for AI::get_open_spots()
Implemented a new minimax.
Speed hacks to minimax.
Added comprehensive AI vs AI testing.
Mark AI comprehensive testing as slow.
Add a Rakefile and add rake to the project.
Use rake to run tests, not rspec.
Remove evaluate_board().
Run the comprehensive AI vs AI testing fewer times.
Added Human and spec.
Human#move() makes a move on the board.
Test Human#move() runs until the human picks a spot on the board.