Do not apply padding to code blocks

Fixes extra padding in the first line of the code block:
![code blocks](http://i.imgur.com/xkDBgpJ.png)

This was a regression introduced by https://github.com/es6rocks/es6rocks.github.io/commit/db8c90b1b06453f08b7607d052a7cfc566871acb / https://github.com/es6rocks/es6rocks.github.io/commit/60df10fe9ceaf0778fa6716f99ce5780da3a3140