Add spacer between nav-tabs

Fixes #408.

This adds a spacer between the nav-tabs:
![screenshot 2014-07-09 22 46 28](https://cloud.githubusercontent.com/assets/5510679/3534260/0f74365a-07e5-11e4-90af-66febe3fd296.png)

It also rounds the unnecessarily long digits/decimals.