Issue2/create users

This PR adds the user model, routes, and views. It follows the lessons in [Node.js, MongoDB, and AngularJS Development](http://www.amazon.com/Node-js-MongoDB-AngularJS-Development-Developers/dp/0321995783/ref=sr_1_1?ie=UTF8&qid=1414077866&sr=8-1&keywords=nodejs+mongodb+and+angularjs) by Brad Dayley