groovy support

Proof of concept groovy support - just shows your framework will work with groovy as well as java
(java syntax is for the most part valid groovy, so the helloworld example is valid as a groovy file)


This will rerun `ps aux` on every block read, so the output may change mid-way and produce broken output. I think this is overkill for a sample filesystem. Having a sample `ps aux` output taken once at start time is good enough.