Spelling fix
Started implementing AI
Human and computer inherit from player
Added executable runner
Started moving player code into human/computer subclasses
Reduced player's dependency to board
Temporarily re-coupled board with player. Created cell class. Started refactoring computer.
Introduce basic pick_corner method
Randomly picks from available corners
Added sides methods to method cell and computer_player
Updated AI with opposite fork strategy
Updated AI to take winning moves and avoid losing
Removed interaction from test
Removed interaction from test
Updated specs
Cleaned code presentation
Added EMPTY_CELL constant
Added further case scenarios for the AI
Minor refactoring
Updated total_markers method