Declare sphinx-me as an extra dependency

[aaugustin]

Hello,

Most users of django-overextends don't need sphinx-me because they won't build the documentation.

https://packaging.python.org/requirements/#install-requires states that install_requires "should be used to specify what a project minimally needs to run correctly".

https://github.com/pypa/sampleproject/blob/cec59671175bc2c86563ac80c90ba28b068a1335/setup.py#L78-L91 suggests that you could put sphinx-me in extras_require instead of install_requires.

Thanks!

[aaugustin]

I assume that sphinx-me is in setup.py to get an automagic setup. Its readme suggests that you could achieve the same effect with a requirements file.

[blag]

This is fixed in master but hasn't been released to PyPI yet. @stephenmcd If you have some time can you create a new PyPI release?