UPDATED the code to match the CakePHP coding standards. Passes 'phpcs
--standard=CakePHP' test

- Added a method called generateTreeArray() under
/lib/Cake/Model/Behavior/TreeBehavior.php. Allows you to create a
hierarchical array list of the records

- Added a testGenerateTreeArray under
/lib/Cake/Test/Case/Model/Behavior/TreeBehaviorNumberTest.php to test
the generateTreeArray() method