Added "shade" goal to build jar with all dependences

I had problems with my Grails app to run karma with this library. I found that if I **copy jar with all dependencies** (like junit-karma-testrunner-1.3-SNAPSHOT-all.jar) to my lib project all works ok.

So, I add the **"shade"** maven plugin to buid this all-in-one jar with: **mvn package** command.

This command generate **target/junit-karma-testrunner-1.3-SNAPSHOT-all.jar**