ReadTheDocs version does not match repository

[chbrandt]

Package version (if known): current

Describe the bug

In the contributing (rtfm) page, pull request guidelines (https://invenio-oauthclient.readthedocs.io/en/latest/contributing.html#pull-request-guidelines), there is a link to Travis that is broken. Whereas in the contributing (github) document (https://github.com/inveniosoftware/invenio-oauthclient/blob/master/CONTRIBUTING.rst) the corresponding link points to GitHub CI workflows.

Also, I suppose the Python versions therein listed (2.7, 3.3, 3.4 and 3.5) is outdated.

Steps to Reproduce

1. Go to https://invenio-oauthclient.readthedocs.io/en/latest/contributing.html#pull-request-guidelines
2. Click on the link (currently, https://travis-ci.com/inveniosoftware/invenio-oauthclient/pull_requests)
3. See error

Expected behavior

To land on a working page after clicking the above mentioned link.
Regarding the Python versions invenio-oauthclient should support I would not expect to see 2.x but 3.x anymore (for new features, at least).

Additional context

Checking the version of the latest version of the docs, at https://readthedocs.org/projects/invenio-oauthclient/, I noticed the latest version was built 2.5+ years ago.