storycap: Cannot screenshot multiple stories with addDecorator

First of all, need to say this is a great add-on. Thanks!

Issue: When looping over stories, addDecorator seems to get stuck after a single story. It will only generate the images for the one story.

As mentioned by @gcazaciuc in #3, it would be very handy not to have to decorate every story manually.

This does not work:

storiesOf('corp-site/atoms/Button', module)
  .addDecorator(withScreenshot(getScreenshotOptions))
  .add('with Black and Active', () => (
    <Button color="black" isActive>Button</Button>
  ))
  .add('with White and inactive, also inaccessible', () => (
    <Button color="white">Button</Button>
  ))
  .add('with Purple and inactive', () => (
    <Button color="purple">Button</Button>
  ))

It will only take screenshots of the first story: with Black and Active.

It would be great to be able to use the addDecorator globally within the config to take screenshots of all stories that are being imported and looped over.