DOC: add Sphinx roles for DOI and arXiv links

[ev-br]

This way, correct hyperlinks are generated automagically in the docstrings.

[larsoner]

Could this be put in numpydoc instead so that other projects can more easily make use of it?

[pv]

I think inclusion in numpydoc can be considered as a separate issue.

[ev-br]

My reading of numpy/numpydoc#34 is that it's not wanted in numpydoc. I'm happy to redirect it otherwise.

[larsoner]

Yeah I agree after reading that issue

[rgommers]

Looks fine to me to add this, quite small and makes the docs more uniform.

Can you add a link to where you found this code? A search for doi_role or doilinks doesn't lead me to the right place.

[ev-br]

It's from https://gist.github.com/jonls/b910afc46473b02597c4
The link was hiding in the commit message, and numpy/numpydoc#34 (comment)

One search line which finds it is "DOI role Sphinx".

For completeness, I'll note that networkx has something similar, https://github.com/networkx/networkx/blob/master/doc/sphinxext/customroles.py

[rgommers]

Thanks, LGTM.

[larsoner]

LGTM +1 for merge