Updating to the latest roaring + minor fixes.

This is a minor update that uses the new roaring package directly from the maven repository.

I have also fixed some minor code issue. E.g., 

1) when warming up, it is fine to require a 1s delay... but not a 1s delay *per* bitmap

2) when warming up, you want to put a strict bound on how many iterations are done...  otherwise the code could conceivable run forever (on a fast machine).