UserList
  - initialize
  - attributes...
  - Operations (ex. next_page returns the next UserList object)
  - Users
  - Load data
    - URL
    - Cache
      - File (JSON)
      - Database
      - Memcache

User
  - attributes...
  - Crud operations
  - Load data
    - URL
    - Cache
      - File (JSON)
      - Database
      - Memcache