Hosted documentation and links are not up-to-date

[joseph-sch]

Hi, I'd like to suggest a few fixes that make it difficult to figure out that the project is still active and to browse its updated documentation:

1. The "latest" documentation at https://python-quantities.readthedocs.io/ dates from July 2018 (version 0.12.1+6.g1ef120b), and no released version beyond 0.12.1 is available there - is there a way to publish the newer releases and the actual "latest"?
2. In the "About" section of the GitHub repository, the link points to https://pythonhosted.org/quantities/ - which hosts documentation of version 0.10.0 from September 2011 - could the link be removed or changed to where the most up-to-date documentation is hosted?
3. In the PyPI page, the "Homepage" link points to http://python-quantities.readthedocs.io/, and there is no link to the GitHub repository - I would suggest that the "Homepage" link or a new "Source" link point to the GitHub repository, and a "Docs" or "Documentation" link point to the hosted documentation, provided it is updated