Updating documentation for Convertible#do_layout

Making it clear that this method doesn't just work on posts

lib/jekyll/convertible.rb

@@ -34,15 +34,14 @@ def transform
       end
     end
 
-    # Add any necessary layouts to this post
+    # Add any necessary layouts to this convertible document
     #   +layouts+ is a Hash of {"name" => "layout"}
     #   +site_payload+ is the site payload hash
     #
     # Returns nothing
     def do_layout(payload, layouts, site_payload)
       # construct payload
       payload = payload.merge(site_payload)
-
       # render content
       self.content = Liquid::Template.parse(self.content).render(payload, [Jekyll::Filters])
       self.transform
@@ -60,4 +59,4 @@ def do_layout(payload, layouts, site_payload)
       end
     end
   end
-end
+end