Preliminary Addition of CosmoSim Simulation Database Query Tool

This it my first pull request of the addition of simulation datbase query tools to astroquery. As it stands, things are in rough shape, but I welcome all comments, concerns, and tips. Thanks!
At the moment this pull request is failing on travis-ci because of this import:
https://travis-ci.org/astropy/astroquery/jobs/29834138#L1080

I don't know if it's worth fixing at this point or if this needs debugging first.