Re list bug fix

Fixes oja-list-bug #184

Also changes the _amd.html_ example not to use custom elements, as this caused issues when testing this (_NSERROR_ when doing `insertOrderedList` with the caret at the end of a 1 line paragraph).
I’m a little unsure about using `textContent === ''`. What if you had:

``` html
<ul><li>1</li></ul>
<p><blockquote></blockquote></p>
```

Of course this wouldn't be HTML produced by the Firefox bug you mention. In this case, you would want the P to be retained.

We know the Firefox bug inserts `<p></p>` with no BR element, so we could just check for `childNodes.length === 0`.