refactor display_board and fix #marked? bug
refactor first computer class test
refactor and generalize board methods
redo of win condition methods to fit more general API, needs refactoring
fix broken computer tests
added #corners method to board for previously failing computer test
fix game_loop error
move InvalidCoordinateError to Board
remove extraneous forwarded methods
remove GameState
remove superfluous GameState calls from board_test
remove GameState from Computer
last traces of GameState removed
GameState files removed
move InvalidActionError into Board
remove Tile class completely
generalize board tests