[not ready] stats warnings

fix https://github.com/mapbox/mapbox-studio/issues/1016
![screen shot 2014-11-14 at 7 01 29 pm](https://cloud.githubusercontent.com/assets/108094/5055423/b39745ce-6c30-11e4-8a26-3b12ff586ad3.png)

![screen shot 2014-11-14 at 7 01 42 pm](https://cloud.githubusercontent.com/assets/108094/5055424/b3a033be-6c30-11e4-9e74-9e56b80c4729.png)

Todo:
- [x] Code/style cleanup
- [x] Consistify UI with print warnings

Wasn't sure about this so I sketched an alternative: https://github.com/mapbox/mapbox-studio/pull/1022