corrected empty square contents
added move method to Piece
Pawns return true to valid_move? on ordinary motion
added additional testing to pawn movement
restructured pawn movement tests
left note to add additional movement tests
added ordinary rook movement validation
added ordinary bishop movement validation
added ordinary queen movement valiation
added ordinary knight movement valiation
added ordinary king movement valiation
improved clarity of knight movement
added ability to check if an index is on the board
made squares_between functional for horizontal and diagonal moves
made squares_between functional for diagonal moves
added ability to check if there is a piece between two locations
refactored valid_move? across all classes to check if pieces are in between
edited pawns to allow diagonal moves to take pieces
edited Piece move method
added ability to move pieces on the board