Edit this page link for standards broken in planemo docs

[peterjc]

1. Goto http://planemo.readthedocs.io/en/latest/standards/docs/best_practices.html
2. Click the link "Edit on GitHub"
3. Goes to https://github.com/galaxyproject/planemo/blob/master/docs/standards/docs/best_practices.rst
4. Observe Error 404 page.

This is included from https://github.com/galaxy-iuc/standards/blob/master/docs/best_practices.rst in the planemo git repository, but that does not get handled automatically by GitHub.

Likely the "Edit on GitHub" definition needs to be special cased for everything under docs/standards/

[jmchilton]

I think this would require basically following the steps outlined in this comment for deleting that link https://github.com/sphinx-doc/sphinx/issues/2386#issuecomment-217861381 - but instead of using a new breadcrumbs file for deletion we would need to use it to target multiple repositories.