Use kramdown for Markdown, otherwise maruku will be used.

postmodern · postmodern · commit a0aeafe1ab55 · 2011-08-04T19:07:10.000-07:00
diff --git a/_config.yml b/_config.yml
@@ -1,4 +1,5 @@
 auto: true
 server: true
+markdown: kramdown
 permalink: date
 pygments: true
