Post tidyverse description cleanup

DESCRIPTION

@@ -9,38 +9,24 @@ Depends: R (>= 3.1.0)
 URL: https://github.com/hadley/r4ds
 Imports:
   bookdown,
-  broom,
   condvis,
-  dplyr,
-  forcats,
   gapminder,
-  ggplot2,
   ggrepel,
   hexbin,
-  hms,
   htmltools,
   htmlwidgets,
   jpeg,
-  jsonlite,
-  leaflet,
-  Lahman,
-  lubridate,
   knitr,
+  Lahman,
+  leaflet,
   maps,
   microbenchmark,
-  modelr,
   nycflights13,
   png,
   pryr,
-  purrr,
-  readr,
-  shiny,
-  stringr,
-  tibble,
-  tidyr,
+  tidyverse,
   viridis
 Remotes:
-  hadley/lubridate,
   hadley/ggplot2,
   rstudio/bookdown,
   rstudio/rmarkdown