Added missing warning to vagrant provisioning script.

Author: mboersma

contrib/vagrant/provision-controller.sh

@@ -103,3 +103,6 @@ if [ $? -eq 0 ]; then
   echo_color "Site object updated."
 fi
 popd
+
+# Need Chef admin permission in order to add and remove nodes and clients
+echo -e "\033[35mPlease ensure that \"deis-controller\" is added to the Chef \"admins\" group.\033[0m"