Updates TODO.md
Adds BoardTest::testPieces
Satisfies BoardTest::testPieces
Refactors Board->positions to be Board->pieces
Fixes comments
Updates TODO.md
Adds PieceTest::testKing
Satisfies PieceTest::testKing
Adds assertion to PieceTest::testKing

+ Piece on board with no King has no King
Adds assertion to PieceTest::testKing

+ Piece without a board has no King
Satisfies PieceTest::testKing: Piece without a board has no King
Updates assertion in PieceTest::testKing

Make sure we are getting the right color no matter how the pieces are
ordered inside the board.
Satisfies PieceTest::testKing to get right color
Updates TODO.md
Adds PieceTest::testCheck

+ King should be in check
Satisfies PieceTest::testCheck: King should be in check
Adds assertion to PieceTest::testCheck: King should not be in check
Updates TODO.md