When not_found, send to different action so status code

It seems when send_file is called, it defaults to 200 even if it's changed to be 404. Not sure why this is and I couldn't find a way to avoid it from happen unless I send it though a different action. Now when a page is not found, it returns a correct 404 status code.

@jeffvincent 
This sets the status code to be 404 and tell the browser it was not found.