Fix documentation and add note about data range representation cludge

Change-Id: I1d4e9926e167963caedc547205a2c0cecf604ae8
diff --git a/R/visitssummary.R b/R/visitssummary.R
index 648c01b..3b99349 100644
--- a/R/visitssummary.R
+++ b/R/visitssummary.R
@@ -9,12 +9,12 @@
 #' @param period       \code{day}, \code{week}, \code{month} or \code{year}
 #' @param date         date range (see \url{https://developer.matomo.org/api-reference/reporting-api})
 #' @param filter_limit defines the maximum number of rows to be returned
-#' @param accessToken  API Authentication Token - you can get this in your
-#' matomo interface under Settings -> Personal -> Settings -> API Authentication Token
 #' @param removeFirst  logical that determines whether the first row of each site should be removed (to account for incomplete periods)
 #' @param removeLast   logical that determines whether the last row of each site should be removed (to account for incomplete periods)
+#' @param accessToken  API Authentication Token - you can get this in your
+#' matomo interface under Settings -> Personal -> Settings -> API Authentication Token
 #' and pass it here, or you can make it persistent with \code{\link{persistAccessToken}}.
-#' @return data frame
+#' @return Data frame with visits summary as returned by matomo. Note that the \code{date} column in the returned data frame refers to the first day of the respective period.
 #'
 #' @import httr
 #' @importFrom jsonlite fromJSON