More rules added

Current Rules:

- Must be the color's turn to move that piece
- Can not move a pinned piece
- Can not move if move doesn't solve check
- Can not move into check
- Check mate

-- Please report bugs
-- Note:  A piece exists after being captured.  There may be times I
have forgotten to check if a piece is captured before calculating if any
of it's moves matter.  I think I've found the major ones

-- TODO

- En Passe
- Castling

- Create a Move class
- The game keeps a list of moves, for undo-redo purposes
- A save game could theoritically be this move list.  The Game makes a
new game (pieces at starting position), and then goes through the move
list making the moves.  The result is the current board state.

- General clean up/ comments so I think others can understand it
- sync with updated SFML files

Notes:
- Checking pins is the last thing that I worked on, and I didn't remove
the cout statements.  If a piece is pinned, you will get a little note
about the direction of the pin, and and a prinout of the map of moves
that would still be possible (those moves are ANDed with the piece's
moves).