Added uppercase option to AutoSlugField.
Tests for separator and uppercase options.
Code of communication event type generated with uppercased letters and
underscore as separator.
Changed setup of functional test in dashboard/communication to be passed
with code populated from name.
Merge branch 'fix/auto-slug-comm-event-type' of git://github.com/vovanbo/django-oscar into vovanbo-fix/auto-slug-comm-event-type
Don't special-case CommunicationEventType code in dashboard views

When sending out notifications, the code is looked up as-is. The
dashboard views previously first lower- and then upper-cased the code. I
fail to see a genuine reason for that, and dislike the added complexity.
More importantly, we don't enforce that the code is uppercased; one
can manually set the slug after all. This means a potential issue with
using slugs that become identical if both are lower-cased. E.g. both
'Foo' and 'FOO' are valid codes, but suddenly the lookup is ambiguous.