[#1261] get_key now pulls from $original instead

This is in reference to issue #1261, where Model->get_key() returns
the key from the $attributes instead of from the $original property.
This breaks the functionality of a model with a primary key that may
change, as the SQL generated will be something like:

UPDATE `model` SET `key` = 'new-key' WHERE `key` = 'new-key';

Which won't update the model in the database.

laravel/database/eloquent/model.php

@@ -544,7 +544,7 @@ abstract class Model {
 	 */
 	public function get_key()
 	{
-		return $this->get_attribute(static::$key);
+		return get_array($this->original, static::$key);
 	}
 
 	/**
@@ -721,7 +721,7 @@ abstract class Model {
 		{
 			if (array_key_exists($key, $this->$source)) return true;
 		}
-		
+
 		if (method_exists($this, $key)) return true;
 	}