Release v4.2: Maintenance release with PyPy compatibility fixes and i…

…nternal simplifications.

Start of development for release 4.3.

Release v4.1: Add finalize_module function and deprecate reclassify_m…

…odules.

Start development for v4.2.

Major refactor of classes.

Candidate 0 for release 4.0.

Start of release 4.1 development.

Special metaclasses for dataclasses. Enhanced immutability decorator.

Candidate 0 for release 3.0.

Start of release 3.1 development.