JS docs: add Options, Methods, Events subsections to nav sidebar

docs/_includes/js/affix.html

@@ -42,7 +42,7 @@ $('#myAffix').affix({
 {% endhighlight %}
 
 
-  <h3>Options</h3>
+  <h3 id="affix-options">Options</h3>
   <p>Options can be passed via data attributes or JavaScript. For data attributes, append the option name to <code>data-</code>, as in <code>data-offset-top="200"</code>.</p>
 
   <div class="table-responsive">
@@ -74,7 +74,7 @@ $('#myAffix').affix({
   </div><!-- /.table-responsive -->
 
 
-  <h3>Events</h3>
+  <h3 id="affix-events">Events</h3>
   <p>Bootstrap's affix plugin exposes a few events for hooking into affix functionality.</p>
   <div class="table-responsive">
     <table class="table table-bordered table-striped">