Add link to Edit on GitHub

_includes/lesson_footer.html

@@ -17,10 +17,12 @@
     </div>
     <div class="col-md-6" align="right">
       <h4>
-	<a href="{{ site.github.repository_url }}/">Source</a>
+        <a href="{{site.github.repository_url}}/blob/gh-pages/{{page.path}}">Improve this page <span class="glyphicon glyphicon-pencil" aria-hidden="true"></span></a>
 	/
 	<a href="{{ site.github.repository_url }}/blob/gh-pages/CONTRIBUTING.md">Contributing</a>
 	/
+	<a href="{{ site.github.repository_url }}/">Source</a>
+	/
 	<a href="{{ site.github.repository_url }}/blob/gh-pages/CITATION">Cite</a>
 	/
 	<a href="{{ site.contact }}">Contact</a>

_includes/navbar.html

@@ -51,7 +51,6 @@
 	{% comment %} Show setup instructions, reference guide, and lesson episodes for lessons. {% endcomment %}
         {% if site.kind == "lesson" %}
         <li><a href="{{ page.root }}/setup/">Setup</a></li>
-        <li><a href="{{ page.root }}/reference/">Reference</a></li>
         <li class="dropdown">
           <a href="{{ page.root }}/" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Episodes <span class="caret"></span></a>
           <ul class="dropdown-menu">
@@ -67,6 +66,7 @@
         <li class="dropdown">
           <a href="{{ page.root }}/" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Extras <span class="caret"></span></a>
           <ul class="dropdown-menu">
+            <li><a href="{{ page.root }}/reference/">Reference</a></li>
             {% for extra in site.extras %}
             <li><a href="{{ page.root }}{{ extra.url }}">{{ extra.title }}</a></li>
             {% endfor %}
@@ -76,6 +76,7 @@
 
 	{% comment %} Always show license. {% endcomment %}
         <li><a href="{{ page.root }}/license/">License</a></li>
+	<li><a href="{{site.github.repository_url}}/blob/gh-pages/{{page.path}}">Edit on GitHub</a></li>
       </ul>
       <form class="navbar-form navbar-right" role="search" id="search" onsubmit="google_search(); return false;">
         <div class="form-group">