[DOC beta] Minor doc fix

Before:

![ember js - ember 2013-12-30 11-35-03](https://f.cloud.github.com/assets/1131196/1823019/5684fc0c-7170-11e3-82bc-2e2dba882bad.jpg)

After:

![ember js - ember 2013-12-30 11-34-34](https://f.cloud.github.com/assets/1131196/1823017/44cfda54-7170-11e3-8abf-c8033aa71d9e.jpg)