Add cron-comments.md

Change-Id: I7b58788c2c39438c6a8142b4ed175de8c6dd7451
diff --git a/.Rbuildignore b/.Rbuildignore
index a918770..6101f5b 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -1,3 +1,5 @@
 ^.*\.Rproj$
 ^\.Rproj\.user$
 ^Readme.md
+^NEWS.md
+^cran-comments.md