BigQuery

## wip.

### Docs: https://stephenplusplus.github.io/gcloud-node/#/docs/master/bigquery

Carrying on from #262. Just opening this so anyone interested can follow along.

`bigquery` vs `bigQuery` ... crap, you're right. I thought our other APIs were one-word, non-camelcase titles, like Datastore (not DataStore), and Storage (not Storage), but now I realize we have PubSub (not Pubsub), so yes, to be consistent, this should be `bigquery`.

re: function and non datastore function, this is because `Datastore` is a container that lets you get through to a Dataset, which is the place where API calls start going off, as opposed to BigQuery, and the other APIs, where the parent classes themselves (BigQuery, PubSub, and Storage), are where API interaction begins. It's a function to allow overriding the global configuration.

I would love to ditch the global configuration override thing -- so, once I say `require('gcloud')({ stuff })`, I don't want to have to use `bigquery().query()`... I want to say `bigquery.query()` -- it's super complicated - could be worth talking about for sure!