Working on module 3

LIST OF CHANGES:
-Chessboard now has movePiece method, which obviously moves pieces across the board
-Game now has a getBoard method
-Added a Player class that has a takeTurn method which moves pieces on the board
-GameManager now has a Player in order to test piece movement, and taking input has been delegated to the Player's takeTurn method
-Piece now has isValidMove, which checks a move to see if it's valid
-Rook movement logic complete