better instructions

Author: okko

bin/compile

@@ -45,6 +45,8 @@ fi
 # and thus the "global names" used before will be for application use.
 if [ -n "$NGINX_VERSION" ] || [ -n "$PHP_VERSION" ] || [ -n "$WORDPRESS_VERSION" ] || [ -n "$S3_BUCKET" ] || [ -n "$WORDPRESS_DIR" ]; then
   echo "Aborting. Env variables controlling buildpack should be prefixed with \"BUILDPACK_\"."
+  echo "This applies to variables NGINX_VERSION, PHP_VERSION, WORDPRESS_VERSION, S3_BUCKET, WORDPRESS_DIR."
+  echo ""
   echo "Rename the variables and push again. For example:"
   echo ""
   echo "    heroku config:set   BUILDPACK_WORDPRESS_VERSION"