Of course save and delete will not work using the fake.json sample but you can check your console network to see the magic happening.
Try this at your own rest server and enjoy.

• $scope.AllUsers.$find()

• 
  Original: {{item.__proto__.fname}} {{item.__proto__.lname}}
  New Data: {{item.fname}} {{item.lname}}
  isChanged: ({{item.$isChanged()}})
  Diff: {{item.$diff()}} Save Delete Custom Action

• $scope.OneUser.$get(1)

• 
  Original: {{item.__proto__.fname}} {{item.__proto__.lname}}
  New Data: {{item.fname}} {{item.lname}}
  isChanged: ({{item.$isChanged()}})
  Diff: {{item.$diff()}} Save Delete