Add test and fixtures for single-part guides
Fix false-positives & test article header

Descendant selector was not being picked up so
target with XPath.
Remove elements associated with multi-part
Correct class name
Fixing issues raised with pull request

Includes spreading this format to programmes.
Adding test for travel advice summary removal
Remove summary heading for single page advice
Merge pull request #293 from alphagov/make-single-part-guide

Make single part guide