Mg center logo nav

![image](https://cloud.githubusercontent.com/assets/2095625/3552269/7eadefd8-08f4-11e4-9429-d20449e0e9f1.png)


![image](https://cloud.githubusercontent.com/assets/2095625/3552275/8f7b975c-08f4-11e4-9c78-92546701c95f.png)

Should this also be `$centered-navigation-padding`?