Add visual indicator that all stream records are erased

This is what it should look like once the data are erased :

![stream_settings__wordpress_develop__wordpress](https://f.cloud.github.com/assets/1933681/1791411/c2dd85ea-698c-11e3-85c1-3fc92c1a35c1.png)


This is ready for review @shadyvb or @fjarrett 

This close #94