Refactored Redcarpet into post.rb

This is an interesting way to go. One suggestion I have is to actually override the 'title' method to return the markdown translated version and have another method called raw_title or something which skips the transformation.  Since most places you'll be calling title you actually want markdown_title, it would make the code easier to read (though maybe slightly harder to debug, since it's easy to forget the transformation is happening). Obviously the same goes for 'body'