README: add coverage badge
diff --git a/README.md b/README.md
index a4e5e29..9288547 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# HttpRouter [![Build Status](https://travis-ci.org/julienschmidt/httprouter.svg?branch=master)](https://travis-ci.org/julienschmidt/httprouter) [![GoDoc](https://godoc.org/github.com/julienschmidt/httprouter?status.svg)](http://godoc.org/github.com/julienschmidt/httprouter)
+# HttpRouter [![Build Status](https://travis-ci.org/julienschmidt/httprouter.svg?branch=master)](https://travis-ci.org/julienschmidt/httprouter) [![Coverage Status](https://coveralls.io/repos/github/julienschmidt/httprouter/badge.svg?branch=master)](https://coveralls.io/github/julienschmidt/httprouter?branch=master) [![GoDoc](https://godoc.org/github.com/julienschmidt/httprouter?status.svg)](http://godoc.org/github.com/julienschmidt/httprouter)
 
 HttpRouter is a lightweight high performance HTTP request router (also called *multiplexer* or just *mux* for short) for [Go](https://golang.org/).