Add links to demo source for a few demos.

_posts/2013-05-01-basic.html

@@ -26,8 +26,20 @@ extraJS: [ "demos/homepage.js" ]
 
 <div class="container">
   <div class="row">
-    <h2>Shuffle.js</h2>
-    <p>{{ site.longDescription }}</p>
+    <div class="col-12@sm">
+      <h2>Source code for this demo</h2>
+      <p>This demo uses the same code as the home page (with the filters).</p>
+      <p>Link to <a href="{{ site.baseurl }}/js/demos/homepage.js">demo source</a></p>
+    </div>
+  </div>
+</div>
+
+<div class="container">
+  <div class="row">
+    <div class="col-12@sm">
+      <h2>Shuffle.js</h2>
+      <p>{{ site.longDescription }}</p>
+    </div>
   </div>
 </div>
 

_posts/2014-03-08-bootstrap3-grid.html

@@ -100,6 +100,14 @@ extraJS: [ "demos/padding-grid.js" ]
   </div>
 </div>
 
+<div class="container">
+  <div class="row">
+    <div class="col-xs-12">
+      <h2>Source code for this demo</h2>
+      <p>Link to <a href="{{ site.baseurl }}/js/demos/padding-grid.js">demo source</a></p>
+    </div>
+  </div>
+</div>
 
 <div class="container">
   <div class="row">

_posts/2017-06-12-flexbox-grid.html

@@ -72,6 +72,15 @@ prism: true
 
 </div>
 
+<div class="container">
+  <div class="row">
+    <div class="col-12">
+      <h2>Source code for this demo</h2>
+      <p>Link to <a href="{{ site.baseurl }}/js/demos/padding-grid.js">demo source</a></p>
+    </div>
+  </div>
+</div>
+
 <div class="container">
   <div class="row">
     <div class="col-12">