Add trailing slash to expected location for gov.uk redirect

The location header includes a slash for the homepage:

    https://github.com/alphagov/redirector/blob/master/tld/gov.uk#L9
Use SSL for single_http_request when scheme is https

This fixes the scenario for the bare domain redirect from https://gov.uk
to https://www.gov.uk/.
Merge pull request #79 from alphagov/update_bare_gov_uk_redirect_feature

Fix test for gov.uk redirect to www.gov.uk