Add various CSS tweaks to viewer.

Closes #149 

### Before
![tn629pk3948-before](https://cloud.githubusercontent.com/assets/96776/4929575/2ca7b42c-6555-11e4-8dcd-0bb824d25fd4.png)

### After
![tn629pk3948-css](https://cloud.githubusercontent.com/assets/96776/4929567/0451aed8-6555-11e4-9630-19b6c9464d96.png)