Adding usage to readme

[matthew-dean]

In case someone else stumbles across this, just having the render function output doesn't seem to help, because doing this doesn't work:

var App = new Vue({
    el: '#app',
    render: render,
  });

// autogenerated render... what now?
function render() { ...}

Can you put something that explains how to turn this particular render function that's output into a usable component?

[matthew-dean]

Never mind! The documentation is unclear, but I figured out you have to write it like this:

var App = new Vue({
    render: render
  }).mount('#app');