Correct a problem when using less than 3 blog article

In this case, the author is (badly) displayed. This patch hard limits blog posts to blog section.

layouts/partials/blog.html

 			</div>
 			{{"<!-- /section title -->" | safeHTML}}
 
-			{{ range first 3 .Site.RegularPages }}
+			{{ range first 3 (where .Site.RegularPages "Section" "==" "blog")}}
 			{{ .Render "article"}}
 			{{ end }}
 
 	</div>
 </section>
 {{"<!-- /blog -->" | safeHTML}}
-{{ end }}
+{{ end }}