Submission:

Please excuse submitting two updates so close together. This update fixes a significant bug for users where options("cores") is not already set.

## Test environments
* local Windows install, R 3.3.3
* local OS X install, R 3.2 
* ubuntu 14.04 (on travis-ci), R 3.4.1 
* win-builder (devel, release, old-release)

## R CMD check results
There were no ERRORs or WARNINGs.

NOTE 
Days since last update: 5