Fix selectedVersion reference bug

Setting library.selectedVersion = library.versions[0] creates an unwanted reference link that results in the [0] element getting overwritten once a new library.selectedVersion is selected. Using angular.copy prevents this unwanted reference.

![image](https://cloud.githubusercontent.com/assets/697848/3374450/667327dc-fbbe-11e3-96a1-0c1236e6980f.png)