Bring breadcrumbs back to detailed guides

The breadcrumbs went away when I did some work to reduce copy pasted
layouts. This should bring them back for just the detailed guidance
layout.

Also added test to ensure the appropriate element does and doesn't exist
where it should and shouldn't.

https://www.pivotaltracker.com/story/show/47697951
Merge pull request #420 from alphagov/fix-breadcrumbs

Tracker: https://www.pivotaltracker.com/story/show/47697951

Bring breadcrumbs back to detailed guides