Add a way to delete articles

Fixes #116

templates/posts/details.html.tera

@@ -22,6 +22,10 @@
         }}</a></span>
         &mdash;
         <span class="date">{{ date | date(format="%B %e, %Y") }}</span>
+        &mdash;
+        {% if is_author %}
+            <a href="{{ article.url}}delete">{{ "Delete this article" | _ }}</a>
+        {% endif %}
     </p>
     <article>
         {{ article.post.content | safe }}