Convert this library to an NPM package

Hi, We've adopted the way of writing unit tests promoted in this repo/blog in our own project over two years ago. It has been very helpful to us and I really like the simplicity it added to our specs. However, it becomes a bit of a problem to rely on this approach when working on multiple projects. If this could somehow be bundled as an NPM library/package, it would be much easier to install/implement these testing utils in new projects.