B3 mobile layout

![screen1](https://cloud.githubusercontent.com/assets/4060105/4217096/1ba3e2de-38e3-11e4-9f2f-5d9b36a184c0.png)
![screen2](https://cloud.githubusercontent.com/assets/4060105/4217097/1baca23e-38e3-11e4-8377-c635dff40890.png)
![screen3](https://cloud.githubusercontent.com/assets/4060105/4217098/1baca4fa-38e3-11e4-87f7-e92f7e61a4e1.png)
![screen4](https://cloud.githubusercontent.com/assets/4060105/4217100/1bada92c-38e3-11e4-83ee-7c5524d935f8.png)
![screen5](https://cloud.githubusercontent.com/assets/4060105/4217099/1bada5b2-38e3-11e4-8bf6-62603739a2a2.png)
![screen6](https://cloud.githubusercontent.com/assets/4060105/4217101/1bae5160-38e3-11e4-87e5-32bf984f5eb5.png)
![screen7](https://cloud.githubusercontent.com/assets/4060105/4217102/1bc12970-38e3-11e4-9ac5-2559c93bd510.png)

why are you removing the class `row` here? That's sort of critical for the `span4` classes to work.