## Test environments
* local OS X (High Sierra, 10.13.6) install, R 3.5.1
* local ubuntu (18.04.1) install, R 3.5.1
* ubuntu 14.04 (on travis-ci), R 3.5.0
* win-builder (devel and release)

## R CMD check results

0 errors
0 warnings
0 note

## Reverse dependencies
There are no reverse dependencies.
