Added GridMap which will be used to store the entities.
Added squareSize field for setting the actual size of each grid square on the screen.
Added a Location class which is a simple (x, y) pair that will be used in the HashMap implementation of GridMap.
Changed the underlying GridMap implementation from a matrix to a HashMap.
Added getLocation() method.
Added move() method that handles moving an entity from one location on the map to another.
Added add() method to Location for doing simple Location addition (will be useful for moving an entity).
Oops. Fixed add() adding y to x.
Modified Game to use the new GridMap as a test.
Merge pull request #2 from mfrancis95/mike

Added GripMap and Location.