Add ability to hide posts from unregistered users.

templates/index.html

@@ -13,7 +13,7 @@
   <div class="post-grid">
     {% for post in posts %}
     <article class="post-card">
-      <div class="post-meta"><span>{{ post.category }}</span><time datetime="{{ post.created_at }}">{{ post.created_at[:10] }}</time></div>
+      <div class="post-meta"><span>{{ post.category }}{% if post.is_hidden %} / MEMBERS{% endif %}</span><time datetime="{{ post.created_at }}">{{ post.created_at[:10] }}</time></div>
       <h2><a href="{{ url_for('post', slug=post.slug) }}">{{ post.title }}</a></h2>
       <p>{{ post.excerpt }}</p>
       <div class="post-foot"><span>BY {{ post.real_name or post.username }}</span><a href="{{ url_for('post', slug=post.slug) }}" aria-label="Read {{ post.title }}">→</a></div>