API docs do not follow the version in conf.py

[jpfeuffer]

Currently API docs will always follow the latest release at the time of the RTD build.
This means the recent releases that I rebuilt due to messed up tagging have a completely wrong API docs.
Also nightly will never have the actual nightly API docs.

@timosachsenberg

[jpfeuffer]

Problem is here: https://github.com/OpenMS/pyopenms-docs/blob/master/docs%2Frequirements.txt#L13

[jpfeuffer]

One should check if you can install it during conf.py based on the version listed there (and if this gets picked up at the point where it parses the docstrings with sphinx-autodoc. Otherwise you need to go back to my branching strategy and make the change in the requirements on each release branch.
This will be messy with the master+ipynb branch though (if you want to maintain example notebooks from previous releases)