Use action for tour items

[erlenddahl]

Since using a <TourItem> block around an element adds a <div> that couldn't easily be styled to not break my layout, I had to add the option for using an action to add tour items.

This pull request adds a "tour" action, so that you can do this:

import { Tour, TourTip, tour, run } from 'svelte-tour';

<main>
    <span use:tour={{message: "A tour item"}}>Blah, blah</span>
</main>

Instead of:

<TourItem message={"A tour item"}>
    <span>Blah, blah</span>
</TourItem>

(Or in addition to, actually -- I didn't remove the TourItem component.)

Also, I added a sequence to the tour parameters so that I can control the sequence of the messages in the tour:
<span use:tour={{message: "A tour item", sequence: 3}}>Blah, blah</span>

This change makes the "data-tour" attribute unneccessary, so I removed it. Items in the store are now saved together with their parameters instead.

Use some of it, all of it or ignore it, no hard feelings any way. :)

[acidlake]

Thanks a lot for this feature, my style was breaking too.