Uses on instead of listenTo for the view show callback.
Improve undefined region show message.

Fixes #1913
adding item-view.jsdoc... again
Add auto addRegions behavior to regionMananger

fixes #1902
fix indentation for destroy method for proper JSON output :neckbeard:
Aliases Marionette as Mn
Updates Module documentation.
Updates Controller documentation.
Replaces slice with _.toArray
Updates docs to use getter methods.
Adds isNodeAttached helper method.
Adds _getNestedView to Layout and Collection Views.
Refactor Application to subclass Object
Refactor Behavior to subclass Object
Refactor Region to sub-class Object
Removes IIFE patterns in source.
Removes slice from jshintrc
Adds deprecation notice regarding Callbacks.
Add JSDOC Preview
Minor: simplify RegionManager emptyRegions