Add @req.session to data in @bind by default

Hi!

Thanks for Creamer - it's great.

I use `@req.session.user` to indicate that user is logged in. In my layout I use that information. So I could pass it to `@bind` in data object. But since I need it always (ie. on every request to every route) I would have to remember that in each call to `@bind`. I saw no other way to make it available for each request (is there?). So I thought that if there is session data it should be available for use in templates.

What do you think?