title: How to update model by id in Backbone.js?
body: <p>I've tried simple example from backbone tutorial and can't get this working</p>
  
  <pre><code>var Person = Backbone.Model.extend({});
  
  var People = Backbone.Collection.extend({
      model: Person,
      url: "http://localhost:3002/people"
  });
  
  var people = new People();
  
  var person = new Person({
      id: 3
  });
  
  person.fetch({
      success: function () {
          person.set({age: 23});
          person.save();
      }
  });
  </code></pre>
  
  <p>I just want to update existing record with id equals to 3 but got an error <strong>A "url" property or function must be specified</strong>. I'm sure that I didn't make mistake when typing this example but it works in tutorial and doesn't work for me. Is it because of some version changes?</p>