docs: issue linking

[dacoex]

The issue link does not work:

Add What’s New section to docs (:issue:`10`)

on page
http://wholmgren-pvlib-python-new.readthedocs.org/en/docfixes/whatsnew.html#new-features

[wholmgren]

#22 isn't even merged yet! I want to keep the issues page focused on the code and documentation that is actually in pvlib/pvlib-python. You can reopen the issue if this is not resolved when it is merged.