Geomfields Reorg for Issue #28

Alec,
I tested this out by spinning up a virtual server without `PostGIS` ( or dependencies ) and without `psycopg2` installed. Running `python example/manage.py test` runs the normal tests without error. Please try this yourself before the merge to verify.

Also, give some thought about the reorganization I did. I changed things from your last commit. If you think this is not the ideal pattern, then I'm wide open to change it. 

The biggest change from your last commit was that I moved geo tests from `geoexample/test/test_geo_modelresource_methods_and_filters.py` back into the `conduit/test/` folder. They felt better there. I figured it's good to keep related tests in the same place since they are all about testing conduit. I then created two TestRunner classes in `conduit/test/testrunners.py` -- one runs the standard tests ( filters out the geo related ones ) and the other only runs the geo tests. These test runners were added to each app's settting file. 

If you think it's better to leave out the test runners in favor of splitting tests up between apps, then I can do that.