Make lib/browser.js a component

lib/browser.js is handy to put inside a script tag, not in a require system. I though it was easy enough to make it a  [component](http://component.io), and it helped me extend superagent and make a [handy http client abstraction](https://github.com/CrowdProcess/superagent-hawk) that works on the browser (don't know any other one currently).