Fixes #570, supports Model#save(key, value)

backbone.js

@@ -291,7 +291,16 @@
     // Set a hash of model attributes, and sync the model to the server.
     // If the server returns an attributes hash that differs, the model's
     // state will be `set` again.
-    save : function(attrs, options) {
+    save : function(key, value, options) {
+      var attrs;
+      if (_.isObject(key) || key == null) {
+        attrs = key;
+        options = value;
+      } else {
+        attrs = {};
+        attrs[key] = value;
+      }
+
       options = options ? _.clone(options) : {};
       if (attrs && !this.set(attrs, options)) return false;
       var model = this;

test/model.js

@@ -331,6 +331,15 @@ $(document).ready(function() {
     ok(_.isEqual(lastRequest[1], doc));
   });
 
+  test("Model: save in positional style", function() {
+    var model = new Backbone.Model();
+    model.sync = function(method, model, options) {
+      options.success();
+    };
+    model.save('title', 'Twelfth Night');
+    equals(model.get('title'), 'Twelfth Night');
+  });
+
   test("Model: fetch", function() {
     doc.fetch();
     ok(lastRequest[0], 'read');