Update doc/README.md

proposed comment about how to use PostGIS 2.0. Currently receiving an error regarding compatibility between django and PostGIS 2.0 "The error was: operator class "gist_geometry_ops" does not exist for access method "gist""
Update README.md
Fixed breaking unit tests
- Set the request on the CachedResourceMixin
- Updated the mixin order for DataSetListView so that key auth is not permitted
- Updated a test to that order of results doesn't matter