support Oauth2's mechanism for refreshing access token periodically -- even though the Wink API doesn't require this yet. I figure, this is going to be implemented sooner or later.
To do this transparently, I had to change how auth information is passed to the Wink object. Now, I am passing a class object that implements a load/save interface (see the persist module for an example), and when the Wink class needs to refresh the access token, it does so and calls the 'save' method to persist the new access token.