Cleaned up Board, wrote Board#dup & Piece#dup
Wrote Board#valid_move_seq? & Board#perform_moves!
Wrote Board#perform_moves
Wrote Game class, game is playable
Harden HumanPlayer
Harden Piece & add private methods
Added Board#winner_color
Changed var name in Board
Improved Game#take_tunr
Created UTF8-based display & general cleanup
Placed Human_Player class into different file