updated release.py readme
updated release.py readme

apache/incubator-singa,nudles/incubator-singa,nudles/incubator-singa,apache/incubator-singa,apache/incubator-singa,nudles/incubator-singa,apache/incubator-singa,apache/incubator-singa,nudles/incubator-singa,nudles/incubator-singa