Merge pull request #1 from deflaux/master

An initial stab at an RDD for Variant Store.
I agree that it's very straightforward. Unfortunately, those classes get regenerated all the time - and then they are automatically pushed to maven. So manually changing them would be quite a pain. 

I'm working on fixing this internally, it's just going to take a while. (The auto-generating code is shared by all APIs at google)