Allow Rails test sessions to generate valid URIs
Allow Rails test sessions to generate valid URIs

It appears that `ActionDispatch::Testing::Integration#build_full_uri`
(in ActionPack 4.2.1 and possibly earlier) requires requested paths to
include leading slashes (which they probably should have done anyway).
Without valid paths, it builds invalid URIs like `www.example.com:80static`,
which cause other parts of Rails to fail when we attempt to generate our static pages.

Not having leading slashes caused generation of static pages to fail
(as described [on the pull
request](https://github.com/ministryofjustice/prison-visits/pull/216#issuecomment-107908617)).

matharden/prison-visits,ministryofjustice/prison-visits,matharden/prison-visits,ministryofjustice/prison-visits,matharden/prison-visits,ministryofjustice/prison-visits