add method isAllowed which is needed afer security patch SUPEE-6285

Author: michael-sauerwald

src/app/code/community/FireGento/AdminMonitoring/controllers/Adminhtml/HistoryController.php

@@ -117,4 +117,15 @@ public function getMonitoringHelper()
     {
         return Mage::helper('firegento_adminmonitoring');
     }
+    
+   
+    /**
+     * Check is allowed access to action - needed afer security patch SUPEE-6285
+     *
+     * @return bool
+     */
+    protected function _isAllowed()
+    {
+        return Mage::getSingleton('admin/session')->isAllowed('system/history');
+    }
 }