Use https for rubygems

HTTP is deprecated
Remove gone.css check

This will let us run the smokey tests against either redirector or bouncer,
because bouncer serves gone.css from stylesheets/gone.css rather than /gone.css
Merge pull request #269 from alphagov/remove_gone_css_check

Remove gone.css check
Correct double-slash in test failure output

The leading slash is already included in the path. This made it harder to
debug.
Remove single quotes from suggested link check

These were failing against bouncer because bouncer's link href is double
quoted. Whilst the intention might have been to look for the URL in the href,
as opposed to anywhere in the page, I can't see what benefit this has, so let's
just assert that the URL appears.
resolve treasury 404s by converting mappings to archive 410 links
Revert "resolve treasury 404s by converting mappings to archive 410 links"

This reverts commit 3c2c8cb290a4c1e84fb5463bd4f1a1511f66ba92.