Refactoring: separated the model layer, with proper injection of its options and the db; one app-wide configuration file with nested objects; debugged the socket.io stuff; added socket authentication; implemented bare beginnings of chat

* people.js was *almost* a cleanly separated model layer, it did almost nothing with req and res. So I took it the rest of the way. All the routes are in app.js, except for that one route hanging out in index.js. See model/people.js. You could have a routes/people.js too if you wanted to get the routes out of app.js
* people.js has a proper constructor and exports a convenience function to call it, so we can inject the database properly when setting it up
* Implemented chats.js too, which provides a model for storing chat remarks
* Implemented chat (it's REALLY basic right now), via the socket connection. Very cool
* Debugged the socket stuff in general. You have to remember all the sockets for all the people who connect and send things to them; otherwise you're just sending to the last guy who connected. Also you have to separately authenticate sockets so you know who you're talking to. 
* There are socket broadcast mechanisms but they don't take authentication into account, so I implemented a simple function that broadcasts only to authenticated users.