Use more sophisticated link and title includes

_includes/link.html

@@ -0,0 +1 @@
+{{ include.url | remove: ".html" | prepend: site.baseurl | replace: '//', '/' }}

_includes/title.html

@@ -0,0 +1 @@
+{{ include.doc.title | remove_first: include.coll.label | remove_first: "/ "  }}

_layouts/sidebar.html

@@ -1,26 +1,21 @@
 ---
 layout: default
 ---
-{% for coll in site.collections %}
-    {% if coll.sidebar %}
-        <h2>{{ coll.caption }}</h2>
-        {% for page in coll.docs %}
-            <h3>{{ page.title | remove_first: coll.label | remove_first: '/ '}}</h3>
-        {% endfor %}
-    {% endif %}
-{% endfor %}
 <div class="container" style="padding-top: 24px;">
     <div class="row">
           <div class="col-md-3" id="toc" style="padding-top: 16px;">
-            {% for group in site.data.sidebar %}
+            {% for coll in site.collections %}
+                {% if coll.sidebar %}
                     <div class="list-group">
-                <a class="list-group-item active">{{ group[0] }}</a>
+                        <a class="list-group-item active">{{ coll.caption }}</a>
-                {% for link in group[1] %}
+                        {% for doc in coll.docs %}
+                            {% capture url %}/{{ site.collections_dir}}/{{ doc.url }}{% endcapture %}
                             <a class="list-group-item" 
-                        href="{% if link.first[1] contains 'http' %}{{ link.first[1] }}{% else %}{{ link.first[1] | prepend: site.baseurl | replace: '//', '/'}}{% endif %}">
+                                href="{% include link.html url=url %}">
-                        {{ link.first[0] }}</a>
+                                {% include title.html doc=doc coll=coll %}</a>
                         {% endfor %}
                     </div>
+                {% endif %}
             {% endfor %}
           </div>
           <div class="col-md-9" id="content">