call Middleware after error Requests

[jxs]

currently a Middleware is only called after a route is found and the handler is successful, so there are situations where the Middleware call function isn't called, and others where you subscribe chain(state) with then, then isn't called:

• 4XX's requests (404 and 405 don't event call the Middleware call function)
• 5XX's requests (if the handler function panics, then isn't called with a HandlerError)