Add testling badge

Author: devongovett

README.md

@@ -4,6 +4,9 @@ Emulates Node's [zlib](http://nodejs.org/api/zlib.html) module for [Browserify](
 using [pako](https://github.com/nodeca/pako). It uses the actual Node source code and passes the Node zlib tests
 by emulating the C++ binding that actually calls zlib.
 
+[![browser support](https://ci.testling.com/devongovett/browserify-zlib.png)
+](https://ci.testling.com/devongovett/browserify-zlib)
+
 ## Not implemented
 
 The following options/methods are not supported because pako does not support them yet.