Some UI enhancements
* Add user link to top_nav for admins or masquerading admins
* Add cancel masquerade to top_nav for masquerading users
* Add name of collection to collection items page
* Add link to edit collection on collection items page
* Changed Add Admin to Add User
* Moved Add User button to top to on user index match style on item index
* Moved New Collection button to top of index like on Items and Users Index
Merge pull request #3 from ndlib/flow-enhancements

Some UI enhancements
added class to model the item json.
change item json to return a hash
change to return a hash and act more like a service
fix the controller to call the new json fields.
Merge branch 'item-json' of https://github.com/ndlib/honeycomb into item-json