adds deprecation note to readme (#299)

README.md

@@ -1,5 +1,6 @@
 # marathon-consul [![Build Status](https://travis-ci.org/allegro/marathon-consul.svg?branch=master)](https://travis-ci.org/allegro/marathon-consul) [![Coverage Status](https://coveralls.io/repos/allegro/marathon-consul/badge.svg?branch=master&service=github)](https://coveralls.io/github/allegro/marathon-consul) [![Go Report Card](https://goreportcard.com/badge/github.com/allegro/marathon-consul)](https://goreportcard.com/report/github.com/allegro/marathon-consul) [![Download latest version](https://api.bintray.com/packages/allegro/deb/marathon-consul/images/download.svg)](https://bintray.com/allegro/deb/marathon-consul/_latestVersion)
 
+> We **no longer develop** this project. If you'd like to take over and continue its maintenance, please fork this repository and let us know by Github issues.
 
 Register [Marathon](https://mesosphere.github.io/marathon/) Tasks as [Consul](https://www.consul.io/) Services for service discovery.