Upgrade blog heading-level

Author: csswizardry

index.html

@@ -70,7 +70,7 @@
 
     <section class=post id=section:articles>
 
-      <h3 class=heading>Web Performance and Site-Speed Insights</h3>
+      <h2 class=heading>Web Performance and Site-Speed Insights</h2>
 
       <p>There are <b>{{ site.posts | size  }}</b> articles on this blog.
       Find them all on the <a href="/blog/">blog page</a>.</p>