Beta 3.2 fix

This addresses #26.

It would seem that rectangles added in 3.2 generate a MSRectangleShape and not a MSShapeGroup. MSRectangleShape objects don't have a style (and therefore no fill) and must first be embedded in a shape group, so it would seem. I've added some logic here to be backwards compatible.

If someone has a better grasp of what's happening here please dive right in.