Updated nav styles for new taglines. Hides taglines on tablet.

Desktop:
![screen shot 2014-03-13 at 3 05 17 pm](https://f.cloud.github.com/assets/583202/2413808/75afa34c-aae2-11e3-8084-5d1dbf43b5a3.png)

Phablet:
![screen shot 2014-03-13 at 3 05 23 pm](https://f.cloud.github.com/assets/583202/2413811/79972322-aae2-11e3-9b40-ec6bfc6c2e54.png)