Support multiple breadcrumb trails

As per Google guidance on [Rich Snippets — Breadcrumbs](https://support.google.com/webmasters/answer/185417?hl=en), Bootstrap currently does not support multiple breadcrumb trails.

I have modified the code to allow a `<div class="breadcrumb">` wrapper with multiple `<ol>` within.

So multiple breadcrumb trail support like:

    <div class="breadcrumb">
        <ol>
            <li><a href="#">Home</a></li>
            <li><a href="#">Library</a></li>
            <li class="active">Data</li>
        </ol>
        <ol>
            <li><a href="#">Home</a></li>
            <li><a href="#">Library</a></li>
            <li class="active">Data</li>
        </ol>
    </div>