Added a Circle CI badge [skip ci]

Author: jkutner

README.md

@@ -1,5 +1,7 @@
 # java-getting-started
 
+[![CircleCI](https://circleci.com/gh/heroku/java-getting-started.svg?style=svg)](https://circleci.com/gh/heroku/java-getting-started)
+
 A barebones Java app, which can easily be deployed to Heroku.
 
 This application supports the [Getting Started with Java on Heroku](https://devcenter.heroku.com/articles/getting-started-with-java) article - check it out.