can you make this: `QueryableStore[-Q, +V]`? I don't see the need to force this to be a subclass of `Store[K, V]` (for instance, I can't write to Google, but I can query it).

Also, and I think Avi asked this, what is the main difference here to: `Readable[Q, Seq[V]]`

Lastly, if we are in the business of making new traits, why not make this: `query(q: Q): Future[Seq[V]]`?

Whatever we decide here should definitely be in storehaus-core.