README.md in instana-1.5.0 vs README.md in instana-1.5.1

- old
+ new
@@ -22,9 +22,10 @@
 [![cuba](https://s3.amazonaws.com/instana/cuba-logo.png?1)](http://cuba.is/)
 [![mina logo 100px](https://cloud.githubusercontent.com/assets/395132/23832558/fcd5bdb2-0736-11e7-9809-3016e89698e2.png)](https://github.com/instana/mina-instana)
 [![sinatra](https://s3.amazonaws.com/instana/sinatra-logo.png?1)](http://www.sinatrarb.com/)
 [![padrino](https://s3.amazonaws.com/instana/padrino-logo.png?1)](http://padrinorb.com/)
 [![rack](https://s3.amazonaws.com/instana/rack-logo.png?1)](https://rack.github.io/)
+[![rack](https://user-images.githubusercontent.com/395132/27842764-27e0e452-610d-11e7-811f-8575f83b8944.png?1)](http://www.grpc.io/)
 
 ## Installation
 
 The gem is available on [Rubygems](https://rubygems.org/gems/instana).  To install, add this line to _the end_ of your application's Gemfile:
 