Update documentation

[MathewBiddle]

The docs are out of date https://pyobis.readthedocs.io/en/latest/

We should update them before GSoC ends.

[7yl4r]

• gh-pages page should be working soon: https://iobis.github.io/pyobis
• https://pyobis.readthedocs.io/ cannot be updated easily
• pypi cannot be used until #44 is merged

[MathewBiddle]

I suggest we remove references to readthedocs for now and then look into how we can delete the site.