Extract `tagged_editions` table to a partial
Add filtering to topic pages
Fix failing ClassificationFeaturingsController test
Adding functional tests for filtering
Scenarios for filtering featured documents on topics
Un-foo/bar tests

Call me a grump, but I find the use of foo/bar in variable names and
values to be unhelpful; there is almost always a more meaningful name/
value that can be used. Also, we shouldn't use instance variables in the
tests where locals will do.
:with_topics trait is redundant if topic supplied
Filtered docs should be scoped to classication

When filtering documents on the topic/topical event featuring page, we
want returned documents to be only those that are actually tagged to the
topic/topical event in question.
Adjusting column spacing to keep it consistent
Merge pull request #1453 from alphagov/filter-documents-to-feature-on-topics-pages

Filter documents to feature on topics pages