Added Remember Me example

It would be great if you could bake any of this into the passport code.  I ended up using the code I found here: http://stackoverflow.com/questions/11199758/node-js-authentication-library-with-persistence-token-functionality/13593575#13593575  Though I realize there are other ways of doing this such as here https://github.com/jaredhanson/passport/issues/93  

Also, the example app.js file is getting fairly large at this point.  I'm not sure if it's best to keep it all in one app.js file for people to read over all in one place or if I should break it up into pass.js, db.js, etc files like I would in real life.

Andrew