Convert views to class based views
Create EmailView, combine with delete view. Also, remove evil tabs
Split inbox address in urls.py to take advantage of the speed of regex
Initial stab at list view of inboxes
Finish off inbox views
Fixes #131
Fix some minor typoes and errors
Viewing emails now works for the most part, as does downloading attachments, plus a few fixes for other CBVs

TODO:
* HTML preference appears to be ignored
* Deleting emails no longer works (we need to change the link to a form)
* Remove last FBVs (blog, settings, possibly errors?)
* Find out where all the pagination numbers went!
Stop counting unread messages and just ★ inboxes that have unread messages

Goes part way to fixing #123
MIME parts don't always have all content* headers
Actually test that there is no text/plain part
Actually get read and seen flags on viewed emails
Make dates on the blog nicer looking

Related to #78
Initial templates for "huh" pages
Learn how to use {% url %} ;)
Finally, after nearly a year, explain what it is that we do.

Fixes Inboxen/infrastructure#7
Add join button to "huh?" page
Centre Join button on huh page
Add LoginRequiredMixin where required
Fix import error