Skip database tests if psycopg2 or db missing
Skip database tests if psycopg2 or db missing

Check if psycopg2 is installed. In setUp() check to see if we can connect
to the test_geopandas database. Skip the read_postgis tests if either
fails.

micahcochran/geopandas,micahcochran/geopandas,jdmcbr/geopandas,kwinkunks/geopandas,geopandas/geopandas,geopandas/geopandas,jorisvandenbossche/geopandas,urschrei/geopandas,geopandas/geopandas,ozak/geopandas,jorisvandenbossche/geopandas,fonnesbeck/geopandas,scw/geopandas,IamJeffG/geopandas,koldunovn/geopandas,snario/geopandas,ozak/geopandas,jorisvandenbossche/geopandas,jdmcbr/geopandas,perrygeo/geopandas,maxalbert/geopandas