Pyramid-debugtoolbar-ajax

* packaging improvements

* black formatting
* upgraded black; 20.8b1
* integrated with pre-commit
* github acitons
* tox
* basic tests
* packaging

bumped requirement for pyramid_debugtoolbar to minimum `add_debugtoolbar_panel` version

- includeme registers the panel via the api method `config.add_debugtoolbar_panel()`

- versionbump to add python3 classifier

- added submit button
- replaced `iteritems` with `items`
- migrated from panels to extra_panels (https://github.com/jvanasco/pyramid_debugtoolbar_ajax/issues/1)