setup.py improvements

[adamchainz]

Rehash of the rejected #73.

I visited the PyPI page as I was looking at dependencies to upgrade and found it a little bare, so I've made these changes:

• Add a link from PyPI direct to the Github repository, so people can find the changelog.
• Use setuptools rather than distutils, because the future is now.

[jackellenberger]

Thanks @adamchainz

We'll test these changes and if all goes according to plan we will merge this in shortly. Thanks for contributing!

[danakatz]

After further discussion, we’ve decided not to make this change — using setuptools adds an extra dependency to our library, and we’d rather not risk the potential complications this may cause for developers who build from our source distribution.

Thanks again for contributing!