Simplify variables in roles/select_involved_roles view
Consistent return types in LimitedVisibilityHelper#visibility_roles_for_current_user
Remove useless '.all' in LimitedVisibilityHelper#visibility_roles_for_current_user
Simplify LimitedVisibilityHelper#role_ids_for_current_viewers thanks to Role#authorized_viewer_ids
Avoid find_by_* methods that are deprecated in rails 4.0
Simplify LimitedVisibilityHelper#visibility_roles_for_current_user even more by requesting things directly through the Role model