Fix author display in single-post blog view.

layouts/blog.html

 <% render 'default' do %>
   <div class="col-md-9 blog doc-content">
     <h1><%= item[:title] %></h1>
-    <aside>Posted at: <%= get_pretty_date(item) %></aside>
+    <aside>Posted at: <%= get_pretty_date(item) %> by <%= item[:author]%></aside>
     <article class="doc-content">
       <%= yield %>
     <article>