0.1.0: First version on GitHUB

0.2.0: First version on PyPI
    Full implementation of a Set and a Mapping using either an AVL or
    a Red-Black binary Tree.
    Coverage > 90%
    Uses pyproject.toml

0.2.1: Cosmetic changes

0.3.0: Add Travis-CI integration
    A bunch of fixes...
    Limit code duplication by using a 2-list for children
    Test usage on Python >= 3.5