Added support for Radar Search in Google Places API.
 * Modified Places object to deal with Radar Search not returning
   basic details like name and vicinity.
 * Added GooglePlaces.radar_search method.
 * FIXME: There a few additional parameters that could be included:
   * https://developers.google.com/places/documentation/search#RadarSearchRequests
 * FIXME: Making these results useful pretty much requires calling
   place_instance.get_details() which is very slow for all 40 results.
 * FIXME: Need to deal with:
   * A Radar Search request must include at least one of keyword, name, or types.