Add regex to exclude tag combiners and guardian weekly subs pages.

Attempt to exclude tag combiners like ``/books/books+tone/reviews`` and subscription trailblock pages like ``/weekly/subscribe/about-guardian-weekly``

CC @guardian/contentapi @guardian/content-platforms
@cantlin Can you adjudicate on this ruby regex, I am slightly confused by http://www.ruby-doc.org/core-2.1.1/Regexp.html