Add npm badge

README.md

@@ -1,4 +1,4 @@
-# browser-env [![Build Status](https://travis-ci.org/lukechilds/browser-env.svg?branch=master)](https://travis-ci.org/lukechilds/browser-env) [![Coverage Status](https://coveralls.io/repos/github/lukechilds/browser-env/badge.svg?branch=master)](https://coveralls.io/github/lukechilds/browser-env?branch=master)
+# browser-env [![Build Status](https://travis-ci.org/lukechilds/browser-env.svg?branch=master)](https://travis-ci.org/lukechilds/browser-env) [![Coverage Status](https://coveralls.io/repos/github/lukechilds/browser-env/badge.svg?branch=master)](https://coveralls.io/github/lukechilds/browser-env?branch=master) [![npm](https://img.shields.io/npm/dt/browser-env.svg)](https://www.npmjs.com/package/browser-env)
 
 > Simulates a global browser environment using [`jsdom`](https://github.com/tmpvar/jsdom).