Lab #4 Checklist:

Here are the things you need to be sure that your program is able to do:

1. Validate board size (it must be an EVEN number  >=4 and <=20)
2. Make sure that the initial pieces are always in the center of the board.
   
3. Print Board with letters are row and column headings
   Print pieces and 'X' in squares that the player could move (Via the check_move function)
4. Get and validate user input for moves
   Allow the user to select a row and column to place a piece.
   Ensure that these are within the boundaries of the board.
   Ensure that the space isn't already occupied
   Check to see if it is a valid move (call check_move)
5. Check the game for winning conditions. (Either the board is full or both players must "pass" because they can't make a move)
6. Ensure that you will call check_move and flip_pieces with the proper arguments in the proper places.
   (See that the stubs work correctly)
7. Be sure you can determine the winner (total number of pieces held by each)
   It is possible to draw!
8. Carefully check to make sure that you meet all register and stack conventions!!!