Incompatible with cookie-session package

[inorganik]

If you are using the cookie-session package instead of express-session, the app works fine until you try to logout.

The logout method calls req.session.destroy() which doesn't exist in the other package, so you get

TypeError: req.session.destroy is not a function

Can we add a check or state that this package needs to be used with express-session? Something like:

if (typeof req.session.destroy === 'function') {
  ...
} else {
 req.session = null;
}

I can PR if you'd like.

[EternalDeiwos]

@inorganik we're looking at reworking the storage and session use soon. We'll keep cookie-session in mind when we do. Stand by for progress!