To be consistent with the rest of Oscar.

This makes more sense than keeping it as a method.

Hattip to @BuddhaOhneHals for doing this in the first place.
Unfortunately, I couldn't (be bothered to) merge the original commit as
the merge conflicts were too painful to resolve - simpler to just
reapply the same change myself.

Fixes #466

Update release notes too.

The parameters have been changed to use request, not request.basket.