Change coordinate system to be sane

To make the coordinates compatible with the format we are supposed to be
using for class (see the link in the syllabus), I flipped the boards y
axis so (0,0) is closest to piece at (0,1), which is game square 1
instead of 4.  This will make the internal calculations easier.  I also
changed your loop counters from i and j to x and y respectively.  Clear
variable names make life easier for your team members :)
Create board class and delegate responsibilities

I created a board class which the gui will delegate responsibility of
maintaining itself and the pieces.

In the future the board object should be able to handle things such as
telling whether a given move is valid based upon a given input.
Additionally, it will handle the execution of moves. issued by the gui.

The screen object will get passed into the board object and likewise to
the piece object per the idea that an object should know how to draw
itself, it just needs to know where.
Merge pull request #1 from hsaloiye/master

Change coordinate system to be sane