This program shows three numbers.  The top and middle number can be 
changed by the user.  The bottom number is always the total of the 
first two.  


* There is a class 'numberbox'
* The class has a method 'inc' that adds one to the number.
* The class has a method 'dec' that adds one to the number.
* The class has a method that draws it on the screen.
* The number turns red when negative, and non-red when positive.

* When I press 'a', the top number goes up by one.
* When I press 'b', the top number goes down by one.

* When I press UP-ARROW, the middle number goes up by one.
* When I press dOWN-ARROW, the middle number goes down by one.

* When I press the 'r' key, the two numbers change randomly.

* The bottom number is the sum of the top and middle numbers.

Out of 11 points.  50% off if not turned in by Tuesday November 23 at 3pm.