Switch to using `totalRows` to determine `tabledata.list` completion.

It looks like BQ is (possibly erroneously?) returning us a `pageToken` when we
do a `tabledata.list` on an empty table. This switches us to just use the
total number of rows fetched; it's slightly less pretty, but much prettier
than infinite loops on empty tables. `;)`

Fixes #15.
Merge pull request #15 from craigcitro/neverending

non-stop runing