Explicitely use and import dplyr::n

Fixes issues with dplyr 1.0

Change-Id: I73c59b00ee8fcc525084767d7520d6dfc4afb311
diff --git a/man/reexports.Rd b/man/reexports.Rd
index 3bce579..919c52c 100644
--- a/man/reexports.Rd
+++ b/man/reexports.Rd
@@ -8,6 +8,7 @@
 \alias{select}
 \alias{group_by}
 \alias{summarise}
+\alias{n}
 \alias{complete}
 \alias{expand_grid}
 \alias{year}
@@ -22,7 +23,7 @@
 \describe{
   \item{broom}{\code{\link[broom]{tidy}}}
 
-  \item{dplyr}{\code{\link[dplyr]{bind_cols}}, \code{\link[dplyr]{group_by}}, \code{\link[dplyr]{mutate}}, \code{\link[dplyr]{select}}, \code{\link[dplyr]{summarise}}}
+  \item{dplyr}{\code{\link[dplyr]{bind_cols}}, \code{\link[dplyr]{group_by}}, \code{\link[dplyr]{mutate}}, \code{\link[dplyr]{n}}, \code{\link[dplyr]{select}}, \code{\link[dplyr]{summarise}}}
 
   \item{lubridate}{\code{\link[lubridate]{year}}}