A few fixes for being able to use complex typeahead menus

Created by: arcanis

+Unit tests, because ❤

With this pull request, you can now make something like :

<input type="text" data-provide="typeahead" data-menu="#all-your-base-are-belong-to-me" />
<div id="all-your-base-are-belong-to-me" class="typeahead">
    <ul class="dropdown-menu" style="display: block;"></ul>
</div>

It wasn't possible before for technical reasons :

• The <div> element was overwrote (.html())
• The typeahead was displayed before typing, because it is using the display:none of the dropdown-menu class. Moving this class downward in the html dom was breaking this.

It's a nice addition for a few use cases : )