Implementing basic open/collapse functionality resolves #13.

app.css

@@ -160,7 +160,8 @@ li {
   height: auto;
 }
 
-.sidebar__level-1 .fa.fa-chevron-down {
+.sidebar__level-1 .fa.fa-chevron-down,
+.sidebar__level-1 .fa.fa-chevron-up {
   margin-right: 1rem;
   font-size: 1.5rem;
   position: relative;
@@ -168,6 +169,7 @@ li {
   display: none;
 }
 
-.sidebar__level-1:hover .fa.fa-chevron-down {
+.sidebar__level-1:hover .fa.fa-chevron-down,
+.sidebar__level-1:hover .fa.fa-chevron-up {
   display: inline-block;
 }

app.html

@@ -81,7 +81,7 @@
                     <i class="fa fa-plus"></i>
                   </a>
                 {{/if}}
-                <i class="fa fa-chevron-down pull-right" style=""></i>
+                <i class="fa fa-chevron-up pull-right" style=""></i>
               </div>
               {{#if children}}
                 <ul>

app.js

@@ -21,6 +21,11 @@ $(function() {
     items: 1
   });
 
+  $('.sidebar__level-1', '.sidebar__level-1--item').on('click', function() {
+    $(this).parents('.sidebar__level-1--item').find('ul').slideToggle();
+    $(this).find('.fa-chevron-down, .fa-chevron-up').toggleClass('fa-chevron-down fa-chevron-up')
+  });
+
 });
 
 var menuObject = {