Turn project into node module

This is a major PR and you might not want it directly. This changes the tests to unit tests that test `schema.js` directly without a server. It also removes everything to do with the homepage and running a server.

This is because of #11 and what I want to do with schematic-ipsum for my own projects: include it as a node module and generate sample data without using the website.

I will create a separate PR for just the website, that then uses this node module.

(I haven't registered anything with `npm` as you own this)

Do you agree with this? Separating the website from the sample generator?

The website project will be cleaner too. I've done this to my own projects ([npmalerts](https://github.com/seriema/npmalerts) vs [npmalerts-web](https://github.com/seriema/npmalerts-web)).