Add site and rdoc output directories to .gitignore.

Author: cfis

.gitignore

@@ -8,6 +8,8 @@ website/_site
 /ext/vc/libxml_ruby_19/Debug
 /ext/vc/libxml_ruby_18/Debug
 /doc
+/site
+/rdoc
 /tmp
 /.idea
 /ext/vc/ipch