Implement linkTo functionality

[jeef3]

As mentioned in #50 this implements linkTo.

It uses the API suggested in the issue, with a couple of additions. The API is:

linkTo(kind: string|func, [story: string|func])

---

The initial suggestion was:

import { linkTo } from @kadira/storybook

storiesOf('Toggle', module)
  .add('on', () => {
    return <Toggle value={true} onChange={linkTo('Toggle', 'off')} />
  })
  .add('off', () => {
    return <Toggle value={false} onChange={linkTo('Toggle', 'on')} />
  });

In addition to this, made the kind optional, so you can linkTo('Toggle') and it will link to the first story in that kind.

Also, while building this functionality I found that there was a use case where the function being passed to the component should accept one or more arguments. That function should then decide where to go based on those arguments. For example, in the Todo Example:

  .add('show completed', () => (
    <div className="todoapp">
      <Footer
        completedCount={10}
        activeCount={4}
        filter={SHOW_COMPLETED}
        onClearCompleted={action('onClearCompleted')}
        onShow={action('onShow')} />
    </div>
  ))

In onShow={action('onShow')}, the action() is passed a constant describing the filter. There is no way to know what the filter will be, so we can't use a string. This is where you can use a function.

onShow={linkTo('Footer', (filter) => {
  switch (filter) {
  case SHOW_ALL: return 'default view';
  case SHOW_COMPLETED: return 'show completed';
  case SHOW_ACTIVE: return 'show active';
  }
})}

[arunoda]

Great work. 💯

I can see the point of passing an function. That's clever.

[montogeek]

It is possible to link storybook components by URL?
Something like http://localhost:8081/?component=MyComponent.

I am asking because I have an idea of link them from a Styleguide, something like:
"Try it in our Storybook"

[arunoda]

@montogeek It'll be available by end of this week.

[montogeek]

@arunoda Marvelous! :D