Unquote response location in assertRedirect

By default Flask url encodes query params which makes testing the location of a redirect slightly awkward.

eg. `self.assertRedirects(res, '/login?next=/somewhere/')` currently fails with 
`'http://localhost/?next=%2Fsomewhere%2F' != 'http://localhost/?next=/somewhere/'`

This fixes the problem by unquoting the response location before asserting equality.