Add test coverage plugin

I propose to add to zeppelin a test coverage in order to see what part of the code is cover or not.
I guess this will give to zeppelin a great value.

![screen shot 2014-12-08 at 5 09 22 pm](https://cloud.githubusercontent.com/assets/3139557/5336431/a40b2b7a-7eff-11e4-9883-fc3ec5d1ae46.png)

run `mvn cobertura:cobertura` or `mvn package` and then check `${buildSubProj}/target/sute/cobertura`