Generate doc versions for tagged releases

[WillemWybo]

Now, the doc websites always shows vlatest. It would be great if it could also show the docs for each tagged release (i.e. v0.9.1)

[WillemWybo]

@jessica-mitchell What is standard practice here? Should we show the latest version or the last tagged version (i.e. the last version tagged on PyPI)?

[jessica-mitchell]

@WillemWybo For NEST our default version is 'stable' which is tied to the most recent release; 'latest' is tied to master so we want to avoid that being the default.

I can update this for NEAT, but we can only add versions of NEAT that have the readthedocs set up. So any version before we created the Read the Docs site cannot be added because they do not have the yaml file that instructs the build process.

[WillemWybo]

@jessica-mitchell Sure, that sounds good. The older versions <= 0.9.2 are deprecated anyway and it's fine to not have those docs.