enabling versioning of documentation:

[ppanero]

Closes #44

Instructions have been moved to the README file.

Open Questions:

• Do we want to push to GH pages? Shall we use another domain? How does this work with GH pages? This should be decided before merging this since it can change the way of deploying/working with it.
• Indentation of the yaml files. This comes from the usage of from ruamel.yaml.util import load_yaml_guess_indent in the install_extras command. Somehow it is interpreting 4 spaces instead of 2.
• The version appears on the install tab instead of the home one. This can be modified in the docs/js/version-select.js and it is easy to do. However, we can just put it somewhere different, top corners? bottom corners? WDYT?

Example:

https://ppanero.github.io/docs-invenio-rdm/0.7.0/ https://ppanero.github.io/docs-invenio-rdm/0.7.1/ https://ppanero.github.io/docs-invenio-rdm/latest/ --> points to https://ppanero.github.io/docs-invenio-rdm/0.7.1/ https://ppanero.github.io/docs-invenio-rdm/ --> redirect to https://ppanero.github.io/docs-invenio-rdm/latest

[fenekku]

We are not using https://github.com/zayd62/mkdocs-versioning/ in the end? Your fix has been merged in. Seems like mike doesn't quite support editing previous documentation which I feel we will need.