- Calling removeGeometry with an invalid index will now raise an IndexError
- Calling collection[0] will return the first geometry in the collection,
collection[1] the second, etc. And negative indices return from the end
of the collection, so collection[-1] returns the last geometry in the collection.
- Geometries can be deleted by calling `del collection[1]` (deletes the
second geometry from the collection). Also supports negative indices
to count from the end of the collection.