reknit README #571

Job	Run time
R-CMD-check / macOS-latest (release)	5m 38s
R-CMD-check / windows-latest (devel)	14m 51s
R-CMD-check / windows-latest (release)	14m 29s
R-CMD-check / windows-latest (oldrel)	15m 47s
R-CMD-check / windows-latest (4.1)	12m 12s
R-CMD-check / ubuntu-latest (devel)	11m 43s
R-CMD-check / ubuntu-latest (release)	5m 40s
R-CMD-check / ubuntu-latest (4.3)	28m 27s
R-CMD-check / ubuntu-latest (4.2)	4m 58s
R-CMD-check / ubuntu-latest (4.1)	4m 49s
R-CMD-check / ubuntu-latest (4.0)	3m 40s
R-CMD-check / ubuntu-latest (3.6)	3m 52s
	2h 6m 6s

Provide feedback