Custom Behaviors Aren't Loading

TL;DR: I have created a custom behavior and done everything I can think of to properly load the class, but I cannot add the behavior to a model due to a classnotfound exception. Where/How should I be loading this custom Behavior?

I am attempting to create a custom behavior -> commentable, to clean up the code project wide for a fairly simple web app.

My thought was to take our currently implemented system (using an endpoint system) to pull comments (our comments table contains all comments, not sepcific to a particular model, so model relationships won't work, unless I am mistaken and a model can have a relationship to something on specific field values -ie the resourceId field matches the class name of the model..)

I have done the following:

• Began migrating the code
• Created a directory in my project /app/behaviors
• Created a file called CommentableBehavior.php to said directory with the following code:

<?php
namespace Phalcon\Mvc\Model\Behavior;

use Phalcon\Mvc\Model\Behavior;
use Phalcon\Mvc\Model\BehaviorInterface;
use Phalcon\Mvc\ModelInterface;

class Commentable extends Behavior implements BehaviorInterface
{

    private $idField = "id";

    public function notify( $eventType, $model ) {

        switch($eventType) {
            case 'afterUpdate':
                // change all the comments for this resource if ID changed

                // change all the comments to deleted if this resource is softdeleted
        }

    }

    public function getComments(ModelInterface $model) {
        $resource_type = get_class($model);
        $resource_id = $mode->readAttribute($this->idField);

         $comments = Comments::find([
        "conditions" => "resource_id=:r_id: AND resource_type=:r_type: AND lft=1",
        "bind" => [
          "r_id" => $resourceId,
          "r_type" => $resourceType
        ]
      ]);

    // Get the comment ordering
    $ordered_comments = Comments::find([
        "conditions" => "resource_id=:r_id: AND resource_type=:r_type:",
        "bind" => [
          "r_id" => $resourceId,
          "r_type" => $resourceType
        ]
      ]);

    $num = 0;
    foreach($ordered_comments as $oc) {
      $comments_order[$oc->id] = ++$num;

    }

    $comments_tree = array();
    foreach ($comments as $comment) {
      $desc = $comment->descendants(null, true);
      array_push($comments_tree, $this->createTree($desc));
    }
    $comments_out->tree = $comments_tree;
    $comments_out->order = $comments_order;

    return $comments_out;

    }

  private function createTree($tree) {
    //same as before
    $currDepth = -1;

    //initilialize result
    $result = array();

    //create path structure for depths
    $path = array();

    //create 'root' node
    $olditem = array('children'=> &$result);

    foreach($tree as $item){
        $item = $item->toAssocArray();
        if($item['lvl'] > $currDepth){
            //remove possible old reference (old depth of other branch
            if(isset($path[$item['lvl']])) unset($path[$item['lvl']]);

            //make sure we have an array entry
            if(!isset($olditem['children'])) $olditem['children'] = array();

            //acquire target
            $path[$item['lvl']] = &$olditem['children'];
        }
        if($item['lvl'] != $currDepth) unset($olditem);
        //set correct target
        $currDepth = $item['lvl'];
        //add item
        $path[$currDepth][] = &$item;
        //copy & remove reference
        $olditem = &$item;
        unset($item);
    }
    //always nice to clean up reference bombs:
    unset($path);
    unset($olditem);

    return $result;
  }

}

• Added the directory to my config->application as "behaviorsDir"
• Added the directory to the loader ($loader->registerDirs( ... ) );
• Updated a model to include:

use Phalcon\Mvc\Model\Behavior\Commentable;

...

  public function initialize()
  {
    $this->setConnectionService('newsdb');
    $this->setSource('wp_posts');
    $this->belongsTo("post_author", "NewsAuthor", "ID");
    $this->hasMany("ID", "NewsMeta", "post_id");
    $this->belongsTo("ID", "NewsTermsRelationships", "object_id");

    $this->addBehavior(new Commentable());

    }

The problem that I am running into is that the behavior isn't adding because of a class not found exception:

 PHP Fatal error:  Class 'Phalcon\\Mvc\\Model\\Behavior\\Commentable' not found in

So, my question is Where should I be saving custom behaviors so they can be used in my app

I have searched the documentation/web and haven't been able to determine where I am going wrong!