initialized starter methods
implements building and filling a board with pieces
implements slide_moves
implements jump_moves
implements perform_slide and perform_jump
implements perform_moves and all underlying methods
implements piece promotion. will now error for move seq. that cont. after piece promotion
fixes bug where promoted pieces couldn't move in reverse.
init game.rb
init player.rb
init turn seq
init win? logic. implements all_pieces method
implements no_moves?
draw?
implements user input
fixes take_input to validate input properly
implements basic GUI
implements forced_jumping game variant