* Added required dependency setuptools to install_requires
* Remove optional dependency ipaddress from install_requires
* Created extras_require in setup.py. The optional dependencies should
not be included in install_requires so that users can either install
forked dependencies or remove problematic ones. Updated documentation to
detail how to install these optional dependencies.
* Fixed README badge
Refs:
* https://dev.deluge-torrent.org/ticket/3470
* https://dev.deluge-torrent.org/ticket/3282
* https://dev.deluge-torrent.org/ticket/3353
- Use sphinxcontrib.spelling with custom wordlist.
- Skip the checking of the modules documents as they raise
false-positives.
- Add a setup.py spellcheck_docs command.
- Fix spelling and other issues.
- Add a doc favicon.
