Add istanbul to Testing

readme.md

@@ -309,6 +309,7 @@ Inspired by the [awesome](https://github.com/sindresorhus/awesome) list thing.
 - [tape](https://github.com/substack/tape) - [TAP](http://testanything.org)-producing test harness.
 - [Mocha](http://visionmedia.github.io/mocha/) - A feature-rich test framework making asynchronous testing simple and fun.
 - [loadtest](https://github.com/alexfernandez/loadtest) - Run load tests for your web application, with an API for automation.
+- [istanbul](https://github.com/gotwarlost/istanbul) - A code coverage tool that computes statement, line, function and branch coverage with module loader hooks to transparently add coverage when running tests.
 
 
 ### Minifiers