Django-webmention

Added
- Better documentation about testing
- Coverage configuration

Changed
- Use markdown for PyPI README

Added
- Mention use of `path()` over `url()` in README
- Mention use of new-style `MIDDLEWARE` over old-style `MIDDLEWARE_CLASSES` in README
- Add system check to detect presence of incorrect middleware configuration
- Update imports and other syntax for forward compatibility with Django 1.10+ and Django 2.0+

Changed
- Reworked the unit tests to be runnable under Travis CI to support continuous integration

Changed
- Successful POST requests will now receive a 202 Accepted response rather than a 200 OK response

Added
- Django 1.9 in frameworks listed in setup.py

Fixed
- Errors in documentation

Added
- Webmentions are now available for review in the admin console
- Webmentions are now updated or invalidated when a new webmention notification request is sent
- Thorough unit testing

Added
- Pre-alpha initial release