Use PGDATABASE env

The dbt tests are starting to require that the PGDATABASE environment
variable be set for postgres related testing.
Use rainbow over cm.colors

Sometimes cm.colors chooses white, which doesn't work well on these
particular types of charts.
Merge branch 'master' of github.com:mw2q/dbttools

Conflicts:
	bin/pgsql/dbt-pgsql-plot-database-stats