Releasing version 3.0.0

Version 3.0.0 was made rock solid by adding unit tests using qUnit and Sinon, run by the Karma test runner. This means that, no matter how much we will author the main file, we will always be sure that every function behaves exactly how we want it to, in every browser.

To add tests I had to refactor the code, exporting almost every function, so the interface of the main function has changed from window.picturePolyfill() to window.picturePolyfill.parse().

The tests have highlighted a small bug on IE8, so if you want to support that browser, be sure to update to version 3.