Creates specific error class MyChessError and changes all raises to use it.
Fixes first move functionality for Pawns.
Adds text to display turn color.
Adds en passant functionality to Pawn#moves and Board#move.
Adds castling logic to King#moves and Board#move
Refactors Board#move wrt pawn and king handling.
Adds possibility of stalemate, and displays a message on endgame.
Makes it prettier!
Adds arguments to display.
Cleans up comments, spacing, etc.
Adds simple AI player feature.
Adds save game functionality.
Adds load game functionality.
Adds beep to Check! printout.
Adds pawn promotion to ComputerPlayer, color highlighting for last move.
Adds some refactoring/simplification.