Load flash message using up-flashes

We are using the up-flashes attribute as documented here.

html

    <div class="col-md-3">
        <nav>
            <a href="/unpoly/1" up-target="article:maybe" up-cache="false">1st</a>
            <a href="/unpoly/2" up-target="article:maybe" up-cache="false">2nd</a>
        </nav>
    </div>
    <div class="col-md-3">
        <article>Default Content 1</article>
    </div>
    <div class="col-md-3">
        <div up-flashes></div>
    </div>

[!NOTE]

We use up-cache to prevent unpoly from caching the content. We also set the selector with :maybe to tell unpoly not to throw error because we are not returning any matching element for article.