Switch to Redcarpet for Markdown Rendering.

This gives us Github Flavored Markdown, which is awesome.

lib/redcarpet/render/gitlab_html.rb

@@ -0,0 +1,9 @@
+class Redcarpet::Render::GitlabHTML < Redcarpet::Render::HTML
+  def block_code(code, language)
+    if Pygments::Lexer.find(language)
+      Pygments.highlight(code, :lexer => language)
+    else
+      Pygments.highlight(code)
+    end
+  end
+end