Add indicator about average length of read (at 200 wpm)

source/layouts/post.haml

@@ -17,6 +17,10 @@
             = current_article.date.strftime(blog_settings.date_format)
           - if tags?
             about #{tags}
+          |
+          - words = Nokogiri::HTML::DocumentFragment.parse(yield).search('.//text()').map(&:text).join(' ').split.count
+          = [1, (words / 200.0).round].max # average reading speed as of http://EzineArticles.com/2298503
+          min read
 
       %section.post-content= yield