fix category import when flat catalog is enabled

We should always grab the actual entity table instead of using
getEntityTable on the resource, because that doesn't exist for
flat resource.

Closes #26

code/Model/Import/Entity/Category.php

@@ -210,9 +210,7 @@ public function __construct()
              ->_initCategories()
              ->_initAttributes();
 
-        /* @var $categoryResource Mage_Catalog_Model_Resource_Category */
-        $categoryResource   = Mage::getModel('catalog/category')->getResource();
-        $this->_entityTable = $categoryResource->getEntityTable();
+        $this->_entityTable = Mage::getSingleton('core/resource')->getTableName('catalog/category');
         $this->_dataSourceModel = Danslo_ApiImport_Model_Import::getDataSourceModel();
     }