Use haversine formula to calculate distance from lat/long of trip shape

I noticed that the partial included 'distanceTravelled'. We currently can't support that, so I added some functions which take care of that for us.
![screen shot 2014-11-10 at 4 05 59 pm 2](https://cloud.githubusercontent.com/assets/1977405/4983754/7146a07c-691d-11e4-83e2-d8b1efe90cdb.png)
![screen shot 2014-11-10 at 4 07 48 pm 2](https://cloud.githubusercontent.com/assets/1977405/4983774/a823ec94-691d-11e4-8829-0bd28cf948a8.png)