UI and checkmate working
Begin error handling
Death to .DS_Store
Fixed Error Handling and moved Error classes to separate file
Abstracted Players classes and refactored Error Handling
Break up files
Sid Review
show moves of piece when input one position
fixed movement bug in h column
refactored Piece and subclasses #valid_moves
Ready to test castling
Castling Works, added 'q' exit game
Stalemate.
Write ChessBoard#game_over?
Pawn promotion bug...