Add Slack badge

README.md

@@ -2,6 +2,7 @@
 [![codecov](https://codecov.io/gh/appscode/voyager/branch/master/graph/badge.svg)](https://codecov.io/gh/appscode/voyager)
 [![Go Report Card](https://goreportcard.com/badge/github.com/appscode/voyager)](https://goreportcard.com/report/github.com/appscode/voyager)
 ![Docker Pulls](https://img.shields.io/docker/pulls/appscode/voyager.svg)
+![Slack](https://slack.appscode.com/badge.svg)
 
 # Voyager
 Voyager is a [HAProxy](http://www.haproxy.org/) backed [secure](#certificate) L7 and L4 [ingress](#ingress) controller for Kubernetes developed by