Calculate and display total distance and time

https://trello.com/c/nhdkSdMl/50-display-total-distance-stay-time-and-time-spent-on-the-way

* Remove uniqueness of stop index [:trip_id, :location_id]
* Calculate and display total distance
* Calculate and display total time spent on road
* Calculate and display total stay time of all stops

![total distance and duration](https://cloud.githubusercontent.com/assets/3759510/5165955/1f3dcd54-73b9-11e4-82c8-698df2bedf8b.png)