cran-comments.md

This should fix the rchk warnings.

Test environments

• local OS X install, R-release
• ubuntu 12.04, R 3.1 -> R-devel
• win-builder (R-devel)

R CMD check results

0 errors | 0 warnings | 0 notes

revdepcheck results

I haven't checked the reverse dependencies because the only changes are additional PROTECT().