Set rb_cRenderedShape variably correctly, don't override yet.
Add Transform class with move() method and stubs for other transformations.
Implement Transform.rotate().
Implement Transform.scale().
Implement Transform.mirror().
Improve some comments.
Add missing parameters to Transform.scale().
Add I constant with identity transform.
Add Transform.to_s().
Copy Transform helper transform methods from Shape.
Add Shape.left, .right, .front, .back, .top, .bottom.
Add Transform.inverse().
Add Shape.transform().
Use shape_transform_g to implement Shape.scale().
Add Shape.align() and center alignment points.