Make orgmap.get_org_contributor_locations() more modular

[staeiou]

Currently, orgmap.get_org_contributor_locations() queries the Github API for location data from profiles and geocodes the location data in the same loop. These should be independent functions. Need a function that takes in a dictionary of { free-text location, descriptor } and returns a dictionary of { geoPy Locations, descriptor }. This would let users map any arbitrary list of locations, no matter where they got it.