Test environments

local OS X, x86_64-apple-darwin15.6.0, R 3.5.0
Ubuntu 14.04.5 LTS, x86_64-pc-linux-gnu (via Travis-CI), R-devel and R-release
Windows Server 2012 R2 x64, i386-w64-mingw32/i386 (via AppVeyor), R-devel and R-release
Windows Server 2012 R2 x64, x86_64-w64-mingw32/x64 (via AppVeyor), R-devel and R-release
win-builder, R-devel and R-release

R CMD check results

There were no ERRORs or WARNINGs.