Register email signup routes for topics.

Registers a prefix route for child topics and
deletes the exact route.

The copy to the array is because FOR SOME REASON
mongo/id returns the same item twice during an
each if you modify the item as it passes, with bad
data to boot.

WHY.  WHY.  WHY MONGO WHY.
Remove unused test setup.
Merge pull request #221 from alphagov/register-email-signup-routes-for-topics

Register email signup routes for topics.