theme: default: support disabling itte for individual posts

via per-post theme config

theme/default/post.hbs

@@ -8,11 +8,13 @@
                 <h1 id="paprika-post-title">{{ title }}</h1>
                 <span class="date">{{ format_date timestamp "%e %b, %Y" }}</span>
                 {{{ content }}}
+                {{ #unless theme_config.no_itte }}
                 {{ #if blog.theme_config.itte_url }}
                 <section id="itte-thread" data-path="{{ page.base_url }}{{ page.pathname }}">
                 </section>
                 <script src="{{ blog.theme_config.itte_url }}/itte.js"></script>
                 {{ /if }}
+                {{ /unless }}
             </article>
         </div>
         <div class="toc-wrapper hidden">