use .navbar-right to position the more exhibits dropdown

After:
![screen shot 2014-03-11 at 8 14 33](https://f.cloud.github.com/assets/111218/2386799/f40a6fd8-a92f-11e3-9092-eb1538caeefe.png)
<hr />
![screen shot 2014-03-11 at 8 14 38](https://f.cloud.github.com/assets/111218/2386798/f3f0eb4e-a92f-11e3-830d-af04e73cb232.png)
<hr />
![screen shot 2014-03-11 at 8 14 47](https://f.cloud.github.com/assets/111218/2386797/f3f0e130-a92f-11e3-9a45-361b5fffe2e6.png)
<hr />
![screen shot 2014-03-11 at 8 14 50](https://f.cloud.github.com/assets/111218/2386796/f3ec4602-a92f-11e3-9212-bf8bb4d48561.png)