Update title of default browse category

Fixes #637 

Removes "Browse" from title of the default "Browse All Exhibit Items" category.

![curation_-_curation_-_browse___default_exhibit_-_blacklight](https://cloud.githubusercontent.com/assets/101482/2701747/16da1494-c426-11e3-9fd9-f94efae98970.png)

![browse_exhibit___default_exhibit_-_blacklight](https://cloud.githubusercontent.com/assets/101482/2701755/3e8f94e6-c426-11e3-93a5-362d240b8c2c.png)