Align codeblock margins with paragraph margins

Maybe it is a matter of taste, though, I have aligned the codeblock margins with the paragraph margins.

![screen shot 2013-06-02 at 5 29 08 pm](https://f.cloud.github.com/assets/3098615/596969/09957b36-cbcd-11e2-9f94-2fcda93ca6d5.png)