👌 Support custom format strings on DateTime and Date fields.
See https://github.com/Pylons/colander/pull/318
👌 Support sub-second precision on Time fields if provided.
See https://github.com/Pylons/colander/pull/319
💅 Format Python code of colander to conform to the PEP 8 style guide.
Add some linters (flake8, black and other) into tox.ini.
See https://github.com/Pylons/colander/pull/320