Winston logging support

[niftylettuce]

In Winston we use "warn" as the error type, e.g. logger.warn('something').

In Connect-Flash we use "warning" as the error type, e.g. req.flash('warning', 'something').

Would it be OK with you if I submitted a PR for adding legacy/fallback support so we can use connect-flash with "warn" as an error type?

[jaredhanson]

I'm not seeing how these things are related. It's up to you how you add things to the flash, you can use req.flash('warn', 'something') if you want.