Run a subset of tests against Postgres or docker-galaxy-stable

[jmchilton]

xref #770
xref e4b028d

[jmchilton]

xref galaxyproject/galaxy#4887. It'd be nice to leverage postgres database templates for speed.

[bgruening]

Database templates for postgresql are here. https://github.com/bgruening/docker-galaxy-stable/tree/master/compose/galaxy-postgres

[mvdbeek]

I think we're doing that now.