Don't log "served" messages

[erikdubbelboer]

These messages aren't very useful and are just costly in Google Cloud Logging.

[koenbollen]

Maybe we add an option to logging.Middleware instead? To completely disable the feature (and the middleware only adds the logger to the context).

[erikdubbelboer]

@koenbollen it's your logging package. Adding an option to logging.Middleware would break compatibility. I think that's why you added this logging.IgnoreRequest().

[koenbollen]

We could do:

func Middleware(next http.Handler, logger Logger, opts... MiddlewareOption)

I'm also very ok with making a breaking change on this package. :P