Use H1 headers in <article> sections

Headers are a semantic element that help computers understand the
content. In general, header tags should follow rank order, but the
most important is that the first header inside a section will serve
as the title in a table of contents, etc, but since article sections
stand alone as independent documents, I like the idea of explicitly
starting with H1 tags.

See: http://diveinto.html5doctor.com/semantics.html

layouts/_default/single.html

@@ -2,7 +2,7 @@
 {{ define "main" }}
       <article class="blog-post">
         <header>
-          <h2 class="blog-post-title"><a href="{{ .Permalink }}" title="{{ .Title }}">{{ .Title }}</a></h2>
+          <h1 class="blog-post-title"><a href="{{ .Permalink }}" title="{{ .Title }}">{{ .Title }}</a></h1>
           <p class="blog-post-meta"><time datetime="{{ .Date }}">{{ .Date.Format .Site.Params.date_format }}</time> by <a href="#">{{ .Params.author | default .Site.Params.author }}</a></p>
         </header>
         {{ .Content }}

layouts/_default/summary.html

@@ -1,6 +1,6 @@
 <article class="blog-post">
   <header>
-    <h2 class="blog-post-title"><a href="{{ .Permalink }}" title="{{ .Title }}">{{ .Title }}</a></h2>
+    <h1 class="blog-post-title"><a href="{{ .Permalink }}" title="{{ .Title }}">{{ .Title }}</a></h1>
     <p class="blog-post-meta"><time datetime="{{ .Date }}">{{ .Date.Format .Site.Params.date_format }}</time> by <a href="#">{{ .Params.author | default .Site.Params.author }}</a></p>
   </header>
   {{ .Summary }}