code: public static boolean hashContains(String hash, double lat, double lon) {
          LatLong centre = decodeHash(hash);
          return Math.abs(centre.getLat() - lat) <= heightDegrees(hash.length()) / 2
                  && Math.abs(to180(centre.getLon() - lon)) <= widthDegrees(hash.length()) / 2;
      }
docs: Returns true if and only if the bounding box corresponding to the hash
  contains the given lat and long.
  
  @param hash
  hash to test containment in
  @param lat
  latitude
  @param lon
  longitude
  @return true if and only if the hash contains the given lat and long