Fix to highlight code example

The indent count for code example sould be 4 not 3.

before:
![2013-06-27 18 30 22](https://f.cloud.github.com/assets/290782/715045/add04a1e-df0f-11e2-9d31-04e295b10371.png)

after:
![2013-06-27 18 37 13](https://f.cloud.github.com/assets/290782/715047/b169709c-df0f-11e2-8dc5-2b3f83927d2b.png)