Add non-standard files to .Rbuildignore

Change-Id: Idbad96d41af9cb5f50a1ad428cde73caeeb30d85
diff --git a/.Rbuildignore b/.Rbuildignore
index 91114bf..4ca26d3 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -1,2 +1,4 @@
 ^.*\.Rproj$
 ^\.Rproj\.user$
+^Readme.md
+^examples/