Performance of hits pt1

* 30% improvement on summary (avoid counting things)
* General, smaller improvement on everything else by avoiding N+1
  for each hit row by preloading the host and site for its row
Without adding the `.all` you're just returning an `ActiveRecord::Relation`, which can be seen as a lazily-evaluated thing representing the data you wanted to look at. Then, in the views, when `.any?` is called, it has to evaluate something and does so with a `COUNT` query. That query is as expensive as getting the data itself, and then the views have to get the data itself, so we pay twice. `.all` is just a way of saying "get this stuff now". In this case, given that we're using no parameters, the same effect can be produced with `to_a`. Would you prefer that?