update to roxygen2 6.0 + markdown
diff --git a/DESCRIPTION b/DESCRIPTION
index 5d8f8c6..50986ad 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -22,4 +22,5 @@
     rmarkdown (>= 1.0)
 Suggests:
     testthat
-RoxygenNote: 5.0.1
+RoxygenNote: 6.0.1
+Roxygen: list(markdown = TRUE)