Replace imagelayers.io with microbadger

This replace the badge of imagelayers.io with a badge microbadger.com because imagelayers.io doesn't work anymore through the registry v2 specification and docker hub supports only the v2 spec.

README.md

@@ -6,7 +6,7 @@
 [![Build Status](https://travis-ci.org/containous/traefik.svg?branch=master)](https://travis-ci.org/containous/traefik)
 [![Docs](https://img.shields.io/badge/docs-current-brightgreen.svg)](https://docs.traefik.io)
 [![Go Report Card](https://goreportcard.com/badge/kubernetes/helm)](http://goreportcard.com/report/containous/traefik)
-[![Image Layer](https://badge.imagelayers.io/traefik:latest.svg)](https://imagelayers.io/?images=traefik)
+[![](https://images.microbadger.com/badges/image/traefik.svg)](https://microbadger.com/images/traefik "Get your own image badge on microbadger.com")
 [![License](https://img.shields.io/badge/license-MIT-blue.svg)](https://github.com/containous/traefik/blob/master/LICENSE.md)
 [![Join the chat at https://traefik.herokuapp.com](https://img.shields.io/badge/style-register-green.svg?style=social&label=Slack)](https://traefik.herokuapp.com)
 [![Twitter](https://img.shields.io/twitter/follow/traefikproxy.svg?style=social)](https://twitter.com/intent/follow?screen_name=traefikproxy)