Test environments

local OS X install, R 3.5.1
Ubuntu 14.04 (on travis-ci), R-oldrel, R-release, R-devel
Windows Server 2012 R2 (x64), R 3.5.1
Rhub
- Windows Server 2008 R2 SP1, R-devel, 32/64 bit
- Ubuntu Linux 16.04 LTS, R-release, GCC
win-builder (devel and release)

R CMD check results

0 ERRORs | 0 WARNINGs | 0 NOTES.