Chen calculate distance

https://trello.com/c/e7RgqDWh/49-as-a-user-i-can-calculate-distance-and-time-between-places

![screen shot 2014-11-21 at 10 17 00 am](https://cloud.githubusercontent.com/assets/3759510/5144354/c08fd264-7167-11e4-8a4f-29f9af19a02e.png)