Add gitter button

README.md

@@ -9,6 +9,7 @@ An online certificate authority and related tools for secure automated certifica
 [Contribution Guide](./docs/CONTRIBUTING.md)
 
 [![GitHub release](https://img.shields.io/github/release/smallstep/certificates.svg)](https://github.com/smallstep/certificates/releases)
+[![Join the chat at https://gitter.im/smallstep/community](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/smallstep/community)
 [![CA Image](https://images.microbadger.com/badges/image/smallstep/step-ca.svg)](https://microbadger.com/images/smallstep/step-ca)
 [![Go Report Card](https://goreportcard.com/badge/github.com/smallstep/certificates)](https://goreportcard.com/report/github.com/smallstep/certificates)
 [![Build Status](https://travis-ci.com/smallstep/certificates.svg?branch=master)](https://travis-ci.com/smallstep/certificates)