Feature request: ability to add a callback to send logs elsewhere

[moltar]

Hey, first of all, very good logging module. It reminds me of Log4j and Log4perl.

One nice feature would be to have the ability to add a callback that will fire on every log event that is emitting so that users could sends the logs to remote stores (e.g. Loggly, or HockeyApp).

I tried to achieve this myself by extending, but couldn't figure it out without overloading too many things. I think a callback would be a cleaner solution.

Let me know, and I can maybe send a pull request.

Thanks.