dplyr (>= 0.2), stringr (>= 0.6.2), assertthat (>= 0.1),
lubridate (>= 1.3.3), utils, stats
assertthat (>= 0.1), dplyr (>= 0.5.0), lubridate (>= 1.3.3),
stats, stringr (>= 0.6.2), utils
knitr, rmarkdown, testthat (>= 3.0.0), withr