hide category name for Uncategorized topics while oneboxing

If the topic category is "Uncategorized" then do not show category badge in onebox. Example:

![screen shot 2014-09-04 at 15 12 39](https://cloud.githubusercontent.com/assets/5732281/4147381/e0f25f1e-3417-11e4-9a94-25422a5eeb52.png)