docs(readme): add Greenkeeper badge

greenkeeper[bot] · greenkeeper[bot] · commit 51d89bafab8c · 2017-10-27T11:45:20.000Z
diff --git a/README.md b/README.md
@@ -1,5 +1,7 @@
 # Exoframe
 
+[![Greenkeeper badge](https://badges.greenkeeper.io/exoframejs/exoframe.svg)](https://greenkeeper.io/)
+
 > Simple Docker deployment tool
 
 [![Build Status](https://travis-ci.org/exoframejs/exoframe.svg?branch=master)](https://travis-ci.org/exoframejs/exoframe)
