Initialize the UnifiedSearcher with a Suggester

Pass the instance of the Suggester class into the UnifiedSearcher, so
that we can use it to build search query suggestions.

This way feels cleaner than the existing approach used for combined
search, where the spelling suggestions get appended into what's returned
from the presenter.
Present "suggested queries" in the search presenter

Change the UnifiedSearchPresenter to include a "suggested queries"
array, used to display spelling suggestions.
Unindent the 'private' keyword

My days of artistic license with the Ruby styleguide are over.
Add a unit test for suggested queries
Merge pull request #218 from alphagov/unified-search-suggested-queries

Add suggested queries to unified search