flash on 2013-8-20

HOMEWORK:
1. Repetitium mater studiorum :) Change the background color of grid 
cells to blue.
2. Fix the defect in the Grid class.
3. (Bonus) Add a class Computer to calculate computer moves. The computer
must not loose. (Hint) You will also need to modify mouseDownHandler
function so that it only plays for one side, while computer plays for 
another side. Computer starts second.
@author wvxvw