Finished module 5, realized that I forgot to implement checking for obstructions along a piece's path, so I'll work on that before moving on to module 6

LIST OF CHANGES:
-Chessboard's testMovePiece has been renamed to detectCheck to specify its purpose, also eliminated some redundancy in the movePiece and detectCheck methods
-GameManager now has a single isKingInCheck method that takes a boolean which specifies which king it is detecting check for, rather than two separate check methods