* added black to develop guide
* no need for pep8radius.
* changelog.
* Add pre-commit checkbox.
* Add pre-commit to dev reqs.
* Add pyproject.toml for black.
* Pre-commit config.
* Add black to travis and dev reqs.
* Install and run black in travis.
* Remove black from dev reqs.
* Lower black target version.
* Re-format with black.