Partial support for story with render function

[pocka]

Summary

Add partial support for story that have render function instead of template.
Since Vue.js is not supported custom renderer for now, this changes do hacks: call render function manually with custom createElement callback which returns JSX string.

See: #36

Limitations

• Accessing this in render throws an exception.

  withInfo('summary', (() => ({
    data() {
      return { name: 'pocka' }
    },
    render(h) {
      return h('p', [`Hello, ${this.name}`]) // Error
    }
  })))

• All variables will be evaluated.

  const foo = 3
  return <p>{foo}</p>

  will be

  return <p>{3}</p>

• Functions will be inlined.

  const myFunc = ev => console.log(ev)
  return <div onClick={myFunc}>foo</div>

  will be

  ;<div onClick={function (ev) {console.log(ev);}}>foo</div>