Chen reorder stop

https://trello.com/c/HDn6APsx/45-update-all-stop-orders-after-delete-a-stop

![update all stops order after delete a stop](https://cloud.githubusercontent.com/assets/3759510/5114158/3ec1a078-7004-11e4-970c-606f8a480e59.gif)


I think this should likely be on the trip, not the stop. `trip.update_stops_after(stop)` or similar.