Make django-sluggable uses a slugify function that downcases
Make django-sluggable uses a slugify function that downcases

The django-sluggable settings file by default just replaces spaces with
dashes rather than downcasing as well:

  https://github.com/mysociety/django-sluggable/blob/master/sluggable/settings.py

... so set it to use the default Django slugify function.

hzj123/56th,patricmutwiri/pombola,hzj123/56th,geoffkilpin/pombola,hzj123/56th,hzj123/56th,mysociety/pombola,geoffkilpin/pombola,geoffkilpin/pombola,mysociety/pombola,ken-muturi/pombola,geoffkilpin/pombola,ken-muturi/pombola,ken-muturi/pombola,hzj123/56th,ken-muturi/pombola,mysociety/pombola,patricmutwiri/pombola,ken-muturi/pombola,patricmutwiri/pombola,geoffkilpin/pombola,patricmutwiri/pombola,patricmutwiri/pombola,geoffkilpin/pombola,ken-muturi/pombola,mysociety/pombola,patricmutwiri/pombola,hzj123/56th,mysociety/pombola,mysociety/pombola