// ABS.Backbone.sync
  // Slight modification of default Sync from 0.3.3
  // Set model.request to result of Ajax call
  // -------------

  // Override this function to change the manner in which Backbone persists
  // models to the server. You will be passed the type of request, and the
  // model in question. By default, uses makes a RESTful Ajax request
  // to the model's `url()`. Some possible customizations could be:
  //
  // * Use `setTimeout` to batch rapid-fire updates into a single request.
  // * Send up the models as XML instead of JSON.
  // * Persist models via WebSockets instead of Ajax.
  //
  // Turn on `Backbone.emulateHTTP` in order to send `PUT` and `DELETE` requests
  // as `POST`, with a `_method` parameter containing the true HTTP method,
  // as well as all requests with the body as `application/x-www-form-urlencoded` instead of
  // `application/json` with the model in a param named `model`.
  // Useful when interfacing with server-side languages like **PHP** that make
  // it difficult to read the body of `PUT` requests.
  Backbone.sync = function(method, model, success, error) {
    // Map from CRUD to HTTP for our default `Backbone.sync` implementation.
    var methodMap = {
        'create': 'POST',
        'update': 'PUT',
        'delete': 'DELETE',
        'read'  : 'GET'
    };
    // Helper function to get a URL from a Model or Collection as a property
    // or as a function.
    var getUrl = function(object) {
        if (!(object && object.url)) throw new Error("A 'url' property or function must be specified");
            return _.isFunction(object.url) ? object.url() : object.url;
    };

    var type = methodMap[method];
    var modelJSON = (method === 'create' || method === 'update') ?
                    JSON.stringify(model.toJSON()) : null;

    // Default JSON-request options.
    var params = {
      url:          getUrl(model),
      type:         type,
      contentType:  'application/json',
      data:         modelJSON,
      dataType:     'json',
      processData:  false,
      success:      success,
      error:        error
    };

    // For older servers, emulate JSON by encoding the request into an HTML-form.
    if (Backbone.emulateJSON) {
      params.contentType = 'application/x-www-form-urlencoded';
      params.processData = true;
      params.data        = modelJSON ? {model : modelJSON} : {};
    }

    // For older servers, emulate HTTP by mimicking the HTTP method with `_method`
    // And an `X-HTTP-Method-Override` header.
    if (Backbone.emulateHTTP) {
      if (type === 'PUT' || type === 'DELETE') {
        if (Backbone.emulateJSON) params.data._method = type;
        params.type = 'POST';
        params.beforeSend = function(xhr) {
          xhr.setRequestHeader("X-HTTP-Method-Override", type);
        };
      }
    }

    // Make the request.
    model.request = $.ajax(params);
  };