Auto slide fragments

This is a small addition to allow users to specify a ```data-autoslide``` attribute for fragments which should fix Issue #650, Issue #653,  Issue #744  and would be useful for creating a plugin solution for Issue #724.

Example:
```html
<section data-autoslide="2000">
	<p>After 2 seconds the fragment will be shown.</p>
	<p class="fragment" data-autoslide="10000">After 10 seconds the next fragment will be shown.</p>
	<p class="fragment">Now, the fragment is displayed for 2 seconds before the next slide is shown.</p>
</section>

```