Implement REST Interface for Users

[calebblanchard]

We need to build a REST interface for User data.

Subtasks:

• [ ] Provide Create, Read, Update, and Delete capabilities for User entity
• [ ] Support the JSON format at a minimum, add XML if you think it would be useful
• [ ] Develop a strategy to handle erroneous requests and error conditions scheme and implement it
• [ ] Use either the REST extension for Firefox or Postman (https://www.getpostman.com/) to test your REST API
• [ ] Create a subdirectory called RESTOutput and put screen snapshots of a GET request, POST request, and a request that has an error