Only add the Python 2 SNI-related requirements if using Python 2
Harmonize capitalization in links.
Show header buttons on all speakers page if there are no speakers.

We still want people to be able to import speakers if there aren't
any already, in fact, we particularly want them to be able to!

The nicest way I can think to do this is to include the normal buttons
from the header. It seems a bit cluttered with the 'All Speakers' heading
though, so I've taken that out until there are some.
Move instance home buttons to sayit.

These buttons used to live in the template in sayit.mysociety.org,
for reasons no-one can remember.
If you edit a speaker/section, update the slug.

We already store slug history and redirect appropriately.
Add flake8 running to pre-commit hook.

Couple of fixes thereby.
Simplify section/speaker forms.

Fixes #350.
Alter section editing URL endpoints to match rest.

The other editing endpoints are all singular.
Add sort name to speaker form and use for sorting.

Also lowercase for ordering purposes.
Use patch from MapIt to cope with use of get_queryset.
Remove homepage form top/bottom margin.