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.

should this be `bigquery` to go with all other apis? (all lowercase)? Unfortunately, this means you'll have to update the examples accordingly.

Also, you've defined it here as function, which makes sense, but datastore below isn't a function... so maybe that's an issue that should be raised on the repo?