Adds LIChess class; gets board state from API.
Board state is created by string.
Removes row decoding, superfluous.
Reorganizes methods so that master setup_board calls get_pos and decode.
Board state represented and previously captured pieces added.
LIChessGame now inherits from Game.
Adds specs to ensure decoding works properly, and moves beginning logic to its own file, asking user if they want LI game or their own game.