Optional Rolling Sessions

Included the "rolling" option. In this way if we need any change of the cookie it will be automatically made available.
A typical example of usage is for the "Remind Me" sessions, where maxAge may vary from null to the prefixed amount of time, depending on the user selection.

Usage:
connect()
  .use(connect.cookieParser())
  .use(connect.session({ secret: 'keyboard cat', key: 'sid', cookie: { secure: true }, rolling : true}))