readthedocs.io setup

[MatthiasValvekens]

I have the impression that the documentation for this library on readthedocs.io is not updating. This isn't a massive deal right now since the examples in there are still more or less accurate (at least insofar as the API usage of this library is concerned), but it could cause issues down the road.

It's not 100% clear to me whether the issue has to do with the changes in dependency management, the repo ownership transfer or something else entirely. @danni @kislyuk ?

On a meta level I think we also need to agree how to handle the maintenance responsibility for that external integration :).

[kislyuk]

I'm not sure why it's not updating, but I switched from readthedocs to github pages for docs in my other projects for this reason (API changes and inability to figure out what went wrong when docs would fail to build) and others, and have been very happy. I would recommend we do that here as well.