First pass at allowing filtering by synonyms
Add ability to search by popular synonyms for countries.

Long term we need a better solution that lets us manage synonyms
properly, but this is a first pass to at least enable searching for some
of the most popular.
Update presenter tests following country changes to FTA tests
Fix conflicts with master and update tests

Merge branch 'master' into synonym_searching

Update the travel index presenter tests.

Conflicts:
	test/unit/presenters/travel_advice_index_presenter_test.rb
Merge pull request #289 from alphagov/synonym_searching

Synonym searching on Foreign Travel Advice