Update sessionConfig with missing cookie attribute

This PR updates the Sessions example with actually working code. I've added the cookie attribute to the sessionConfig because it's mandatory at the moment (see [bone.io middleware](https://github.com/techpines/bone.io/blob/master/lib/node/middleware.coffee)) and a small typo is also fixed.

Thanks for bone.io. Looks interesting even tho I've only played around with it a little.