Fix markup to apply syntax highlight

`hbs` is not valid language name.

Before:
![2014-10-15 21 42 20](https://cloud.githubusercontent.com/assets/290782/4645472/569b851c-5469-11e4-83c3-63f8c905639e.png)

After:
![2014-10-15 21 42 29](https://cloud.githubusercontent.com/assets/290782/4645473/59d6174c-5469-11e4-8eef-4f0dd53c24d3.png)