Pytest-check

Fixed

- Support check failures not blowing up if called outside of a test.
- should also fix [85](https://github.com/okken/pytest-check/issues/85)
- thanks [zerocen](https://github.com/zerocen) for the excellent toy example that helped me to get this fixed quickly.

Changed

- changelog.md format. :)
- tox.ini cleanup
- refactoring tests to use examples directory instead of embedding example tests in test code.
- this is easier to understand and debug issues.
- also provides extra documentation through examples directory

Fixed

- Handle cases when context is None

Changed

- Update pyproject.toml to use newer flit
- Changed plugin name from pytest_check to pytest-check.

Added

- Add `raises`

Changed

- Require Python >= 3.6
- Remove old Manifest.in file.

Fixed

- Fix 64, modifications to maxfail behavior.