title: Retrofit returns empty object, but json seems valid
body: <p>This is the json I get from my endpoint. I got it using proxy, so this is exactly what retrofit gets:</p>
  
  <pre><code>{
      "id": 1,
      "email": "jacek@gmail.com",
      "name": "Jacek KwiecieŇĄ",
      "google_plus_id": "117434793312604634191",
      "facebook_id": null,
      "avatar_url": "https://some_url",
      "last_login_at": "2015-06-14T12:36:58.831Z",
      "created_at": "2015-06-14T12:36:58.829Z",
  }
  </code></pre>
  
  <p>I create RetrofitService like this:</p>
  
  <pre><code>private static final RestAdapter REST_ADAPTER = new RestAdapter.Builder()
          .setEndpoint(BuildConfig.SERVER_URL)
          .setConverter(new GsonConverter(new GsonBuilder().create()))
          .build();
  
  public static final Api API = REST_ADAPTER.create(Api.class);
  </code></pre>
  
  <p>Finally here is my model class:</p>
  
  <pre><code>public class User {
      public long id;
      public boolean active;
      public String email;
      public String googlePlusId;
      public String facebookId;
      public String name;
      public String avatarUrl;
      public String coverPhotoUrl;
  }
  </code></pre>
  
  <p>Why would retrofit return me an empty User object? Json is valid and no errors are thrown.</p>