Turn buy.js into require-able file.

[jcblw]

https://github.com/jcblw/Mujo-extension/blob/master/public/buy.js

This is the file that Google gives us to setup IAP but its minified and not fun. It has already been slightly changed but is not great. Optimally we can analyze the file and then refactor it to be more readable, testable, and also be able to require it.

This is potentially something I would like to open-source since I am not able to find anything that does this.

https://www.npmjs.com/search?q=iap%20chrome