Update to v4.8.0

Changelog

v4.8.0 (2020-06-13)

• Support attribute based setters like `argparse.Namespace in set_, set_with, update, and update_with`.
• Fix exception in `order_by when None` used as a sort key. Thanks elijose55_!
• Fix behavior of `pick_by` to return the passed in argument when only one argument given. Previously, an empty dictionary was returned. Thanks elijose55_!
• Officially support Python 3.8.

Reported by: portscout