Puzzle Readme

There are some differences in the posted files in this section from KP's
notes and previously posted Puzzle files:
 
  + PlayPuzzle is the main class.
  + IPuzzle includes a few more methods.
  + The files use PuzzleAs<type> for the name convention.
  + The tile method exists only in PuzzleAsInt.
  + The Array puzzle was originally set up to handle nxn size puzzles.
    The String puzzle could handle 2x2 or 3x3. Currently they are set to 3.
    To change, you need to add another constructor. You should also have the
    user input the size at the command-line.
  + Each class implements its own display method.

As a useful exercise, you should rewrite the classes to be consistent with
KP's notes. Follow the PuzzleAsInt for that consistency.