Since there is no way to override SlugField and AutoSlugField in existing Oscar models, it was decided to pass `allow_unicode` parameter if this setting enable. This allows to achieve backwards compatibility with Django versions under 1.9, when this parameter was not supported yet. If parameter specified in the field expliticly - we do not override it, which allow to control slug fields individually in a normal way. For the reasons, explained above, standard SlugField was replaced with a custom one with the single slight change - control over `allow_unicode` parameter by the mentioned setting.

This removes all the bits and bobs where we referenced South, or added
some code supporting it. Documentation will be updated in a later
commit, together with other Django changes.

TestCase.assertEquals (note the s at the end) has been deprecated.
The only failing tests remaining are CSV related, which is not
surprising.

Tests for separator and uppercase options.

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