namespace turkle's URLs for reverse lookup

[cash]

Looks like @TomLippincott ran into an issue using Turkle as an app due to us not namespacing our URLs:

stats_url = reverse('stats_for_user', kwargs={'user_id': obj.id})

I believe this prevents any other app running from using the key 'stats_for_user'. What I don't understand is why Tom switched from

    return redirect(index)

to

    return redirect(reverse("turkle:index"))

as in the first case index it is a function and shouldn't case any conflicts.

Two relevant commits: 5a529f0, 5045edb