Updates the layout dividers to add more space betwixt them on small screens. Also updates 2nd nav line height.

I had initially overridden the line height and set it to 1 in order to use the same amount of padding on all sides. But when we ran into a scenario where the text inside one of the nav items wrapped I realized that was a mistake, we need that larger default line height. Now that I ditched the `line-height: 1` override I had to decrease the vertical padding to account for it. Here's a screen shot of how it look:

![image](https://cloud.githubusercontent.com/assets/1093373/4388618/57d9b12e-43ed-11e4-9097-6a80aed6b631.png)