Site content is visible only to super admins
Update gems, add spring for faster testing.
Load admin site in users_controller

Should fix Trello card no. 1432
Handle RecordNotFound and attempt to fix the test for destroying users
Admin deleting users: Fix test, remove spurious rescue
Tidy up all these tests, CanCan, etc.
Add support for supplying a block to admin_route_redirect
Update paperclip version dependency
Fix redirect loop. Users can edit sites, sometimes.