news: looser relevancy for entities.

cc @bsstoner @russellholt @nilnilnil @jagtalon 

allow looser news relevancy when we have a good signal that the query contains a newsworthy entity.
`DDG.news_entities` will be set internally.

this is pretty far out of my domain, so if there's a better way to override (not in the technical sense, but in the sense contained herein) `DDG.isRelevant` (or if my JS sucks) please let me know. moreover, not sure who to assign.
You can probably flatten this out by making an array of `entity.splits`.  Also, I'm not sure `entity` is a good name anymore.  Then `array.indexOf` or `$.inArray` would make this really easy to see.