bug#911172 - Changed nav-options from blue to gray

A very simple and quick fix for the Editor and Preview text confusing people that they are links.

<a href="https://bugzilla.mozilla.org/show_bug.cgi?id=911172">Link to the bugzilla</a>

![image](https://f.cloud.github.com/assets/1514285/1277716/b5f5b5e2-2eda-11e3-92b6-d9099e9e5d95.png)