Parallelized version of needlestack.r

[veenarajaraman]

Hi,
We found it useful to have a version of needlestack.r that runs using R's multi-core functionality. I am happy to submit a PR with this script if you could give me the privileges to create a branch on this repo. If this is not feasible we can fork this repo and add our changes to it.

Thank you
Sincerely,
Veena Rajaraman
Senior Bioinformatics Scientist | Bioinformatics
1400 16th Street, San Francisco, CA 94103
https://www.invitae.com/