Add golangci badge (zalando#423)

erthalion · sdudoladov · commit a0e09cd6a636 · 2018-11-27T11:59:59.000+01:00
Since we've connected it, it makes sense also to display the results.
diff --git a/README.md b/README.md
@@ -4,6 +4,7 @@
 [![Coverage Status](https://coveralls.io/repos/github/zalando-incubator/postgres-operator/badge.svg)](https://coveralls.io/github/zalando-incubator/postgres-operator)
 [![Go Report Card](https://goreportcard.com/badge/github.com/zalando-incubator/postgres-operator)](https://goreportcard.com/report/github.com/zalando-incubator/postgres-operator)
 [![GoDoc](https://godoc.org/github.com/zalando-incubator/postgres-operator?status.svg)](https://godoc.org/github.com/zalando-incubator/postgres-operator)
+[![golangci](https://golangci.com/badges/github.com/zalando-incubator/postgres-operator.svg)](https://golangci.com/r/github.com/zalando-incubator/postgres-operator)
 
 ## Introduction
 
