Add Reverse Geocoding API

[jpaye]

Clients are interested in using the reverse geocoding API to convert lat/long pairs to Gro regions

We already have a geocoding API, here we're just making it accessible in the client

• Adds the reverse_geocode_points method
  • Takes a list of points to geocode, returns a list of Gro regions
• Adds tests in both client_test.py and lib_test.py

Tested locally:

>>> client = GroClient()
>>> client.reverse_geocode_points([[33.4484, -112.0740], [42.3314, -83.0458], [-8.8742, 125.7275]])
[{'latitude': 33.4484, 'longitude': -112.074, 'l5_id': 136859, 'l5_name': 'Maricopa', 'l4_id': 13053, 'l4_name': 'Arizona', 'l3_id': 1215, 'l3_name': 'United States'}, {'latitude': 42.3314, 'longitude': -83.0458, 'l5_id': 138067, 'l5_name': 'Wayne', 'l4_id': 13073, 'l4_name': 'Michigan', 'l3_id': 1215, 'l3_name': 'United States'}, {'latitude': -8.8742, 'longitude': 125.7275, 'l5_id': 134452, 'l5_name': 'Turiscai', 'l4_id': 12774, 'l4_name': 'Manufahi', 'l3_id': 1199, 'l3_name': 'East Timor'}]