----------------
- Do not run test suites for Python 2.6 and Python < 3.7 any more.
[rnix, 2022-03-16]
- Replace ``Bases`` wrapper with a ``set`` containing ``derived_members``
to avoid multiple base class iteration.
[rnix, 2022-02-13]
- Only keep most recent instructions on ``Stacks`` when parsing behaviors.
[rnix, 2022-02-13]
- Simplify ``Stacks`` object.
[rnix, 2022-02-13]
- Apply stage 1 and stage 2 instructions in ``plumber.__new__`` instead of
applying stage 2 instructions in ``plumber.__init__``.
[rnix, 2022-02-13]