Make version strings more specific

[timothydijamco]

This is so that for example tarballs generated from ibis-bigquery are of the form ibis-bigquery-0.1.0+2.g1076c97.tar.gz (currently, the version format is just the version number, e.g. ibis-bigquery-0.1.0.tar.gz regardless of which specific commit the tarball is being built from)

The main Ibis repo's setup.py uses versioneer, and we may be able to do something similar here