Now after ConditionalOffer deleted will be deleted related Benefits and Conditions models (through post_delete signal) if they are no longer used by other offers (with exception of custom benefits/conditions). Plus some small changes related to PEP8 and typos.

We only needed it because Django 1.4 shipped with a pretty old version
of six. Support for that has been removed, and Django 1.5 ships with six
1.6.1, which is more current than we required.

This nicely avoids an issue with django-extra-views pinning a six
version which caused the sandbox build to fail:
https://travis-ci.org/tangentlabs/django-oscar/jobs/32223978#L971

Tests for separator and uppercase options.

Taken from django-extensions with some adapting to our needs.