Switch to Redcarpet for Markdown Rendering.

This gives us Github Flavored Markdown, which is awesome.

app/views/wikis/show.html.haml

@@ -9,7 +9,7 @@
 %hr
 .wiki_content
   = preserve do
-    = markdown_to_html @wiki.content
+    = markdown @wiki.content
 
 %p.time Last edited by #{@wiki.user.name}, in #{time_ago_in_words @wiki.created_at}
 - if can? current_user, :admin_wiki, @project