- Correct assertion for Ansible 2.3.0.0 (ansible_distribution_release and ansible_distribution_version were reversed for OpenBSD prior to that version).

- Build on my supported platforms (some don't have properly working Vagrant boxes so they're allowed to fail).

- Add pre-commit check for out-of-date dependencies.
- Add flake8 pre-commit check.
- List roles needed for testing (bootstraping) at
tests/requirements.yml, leave other dependencies at meta/main.yml.
- Update molecule.yml, ansible.cfg for newer versions of Molecule.
- Update documentation, playbook accordingly.

  issues:
  - Missed a blank line between tests in `tests/test_example.py`.
  - Named the assertions task.
- Updated the OpenBSD Vagrant box to 6.0, updated assertion accordingly.