Dynamically generate the JSON files

Hey, I have added json files to generate.js so they are generated together with licenses.

But I have used sync fs methods in few places (reading licenses content), because I was just a lot easier, so I'm not sure if you will like it :)

Issues covered:
#2
#3
since you're not using the extract in `download`, it's probably better to just use `request` directly as it can be a read stream: https://github.com/mikeal/request#streaming