docs(readme): add Greenkeeper badge

greenkeeper[bot] · greenkeeper[bot] · commit e6c6a66e5e33 · 2017-12-29T23:49:24.000Z
diff --git a/README.md b/README.md
@@ -1,4 +1,6 @@
 # JUDGE API SERVER
+
+[![Greenkeeper badge](https://badges.greenkeeper.io/coding-blocks/judge-api.svg)](https://greenkeeper.io/)
 [![CircleCI](https://img.shields.io/circleci/project/github/coding-blocks/judge-api.svg)](https://circleci.com/gh/coding-blocks/judge-api)
 [![Travis](https://img.shields.io/travis/coding-blocks/judge-api.svg?style=flat-square)](https://travis-ci.org/coding-blocks/judge-api)
 
