Working demo:

http://todos-rest-server.appspot.com/


The main difference between appengine-rest-server and Backbone's
expectations for a rest server are that the objects are wrapped.
So we need to change Model.parse() and Model.toJSON() as well as
Collection.parse()

For example, appengine-rest-server expects an object like this:
         {Todos:
           {
             content: 'Buy milk.',
             done:    'false',
             order:   1
           }
         }
Whereas Backbone deals expects models like this:
           {
             content: 'Buy milk.',
             done:    'false',
             order:   1
           }

           
When GETting a collection, appengine-rest-server gives back something like:
        {
            list: {
              Todos: [
                {content: 'Buy milk', done: 'false', order: '1'},
                {content: 'Buy eggs', done: 'true', order: '2'}
              ]
            }
         }
        We need to parse it to look like:
        
         [
           {Todos: {content: 'Buy milk', done: 'false', order: '1'},
           {Todos: {content: 'Buy eggs', done: 'true', order: '2'},
         ]
And there is one other case.  When the collection has only one element, a GET
returns without a list like this:
         {Todos: {content: 'Buy milk', done: 'false', order: '1'}
         So we need to wrap that single object in a list:
         [{Todos: {content: 'Buy milk', done: 'false', order: '1'}]



Another issue is that everything comes back as a string from the server.
For example {"done": false} is returned as {"done": "false"}
So we need to explicitly convert them.  
This is done in the helper function: convertStringToTypes 
which is called in AppengineRestModel.parse()
The attributes to convert have to be specified in AppengineRestModel.attrTypes