Return an iterator tweets from users in these locations.
    See https://dev.twitter.com/streaming/overview/request-parameters#locations
    Params:
        locations...list of bounding box locations of the form:
        southwest_longitude, southwest_latitude, northeast_longitude, northeast_latitude, ...

def track_locations(locations):
    """ Return an iterator tweets from users in these locations.
    See https://dev.twitter.com/streaming/overview/request-parameters#locations
    Params:
        locations...list of bounding box locations of the form:
        southwest_longitude, southwest_latitude, northeast_longitude, northeast_latitude, ...
    """
    if len(locations) % 4 != 0:
        raise Exception('length of bounding box list should be a multiple of four')
    results = twapi.request('statuses/filter', {'locations': ','.join('%f' % l for l in locations)})
    return results.get_iterator()