Implement a sonar processor

Hi, 

We've implemented a way for sputnik to run Sonar-runner to report issues.
We use it in conjunction with sonar-ndepend (https://github.com/criteo/sonar-ndepend) but should work with
all sonar plugins as long as they provides the line information.

Cheers
Is this Sonar dependency? We already use Jackson's ObjectMapper to handle JSON. Is this suitable for you to use Jackson instead of a second JSON dependency?