code: function getFollowers(T, user_id, max_followers, finish) {
    return getFollowersIt(T, user_id, [], -1, max_followers, finish);
  }
docs: /*
  GetFollowers(T, user_id, max_followers, finish)
  Gets all followers of given user and calls the callback with the array of followers.
  Possibly waits until the max #requests/15min rate has passed, so can take a while.