added multi sidebar support

.themes/classic/source/_layouts/post.html

@@ -24,3 +24,12 @@ single: true
   </section>
 {% endif %}
 </div>
+{% unless page.sidebar == false %}
+<aside role=sidebar>
+  {% if site.post_asides.size %}
+    {% include_array post_asides %}
+  {% else %}
+    {% include_array default_asides %}
+  {% endif %}
+</aside>
+{% endunless %}