bundle update acts_as_sane_tree

* this is primarily to get improved 'preloading' functionality I've added recently
* this also updated a few dependent gems.  I am not sure why.
* to disable a deprecation warning message that is now being shown, we are setting config.i18n.enforce_available_locales = true
  * this seems to be a better setting, anyway
  * we don't seem to rely on the previous behavior
  * see http://stackoverflow.com/questions/20361428/rails-i18n-validation-deprecation-warning for more info
remove redundant line
factor identical code into a method
this can't happen
use find_with_descendants
indent only by 2 spaces
avoid unnecessary EntityType lookups

* preload children of associated EntityTypes
* use this preloaded association in Entity#_assign_attribute
typo fix
create new entities with already loaded associations
better preloading in EntitiesController#index

* preload descendant entities (though not associated enums; this will still be a separate query)
* preload all associated entity_types
use update! instead of update_attributes

* update and update_attributes are identical; may as well use the smaller one
* use bang version to avoid silent validation failures