pkg/js: fix readme for pkg/js and prepare another release

pkg/js/README.md

 Methods and annotations to specify interoperability with JavaScript APIs.
 
 *Note: This package is beta software.*
 
 *Note: This packages requires Dart SDK `>=1.13.0-dev.7`.*
 
 ### Adding the dependency
 
 Add the following to your `pubspec.yaml`:
 
 ```yaml
 dependencies:
   js: ^0.6.0-beta
 ```
 
 #### Passing functions to JavaScript.
 
 If you are passing a Dart function to a JavaScript API, you must wrap it using
 `allowInterop` or `allowInteropCaptureThis`.
 
 ### Examples
 
 There is a [full example](https://github.com/dart-lang/sdk/tree/master/pkg/js/example) hosted with the `package:js` source code.
 
 #### Calling methods
 
 ```dart
 // Calls invoke JavaScript `JSON.stringify(obj)`.
-@Js("JSON.stringify")
+@JS("JSON.stringify")
 external String stringify(obj);
 ```
 
 #### Classes and Namespaces
 
 ```dart
-@Js('google.maps')
+@JS('google.maps')
 library maps;
 
 // Invokes the JavaScript getter `google.maps.map`.
 external Map get map;
 
 // `new Map` invokes JavaScript `new google.maps.Map(location)`
-@Js()
+@JS()
 class Map {
   external Map(Location location);
   external Location getLocation();
 }
 
 // `new Location(...)` invokes JavaScript `new google.maps.LatLng(...)`
 //
 // We recommend against using custom JavaScript names whenever
 // possible. It is easier for users if the JavaScript names and Dart names
 // are consistent.
-@Js("LatLng")
+@JS("LatLng")
 class Location {
   external Location(num lat, num lng);
 }
 ```
 
-#### Maps
+#### JavaScript object literals
 
-Dart `Map` objects, including literals, are "opaque" in JavaScript.
-You must create Dart classes for each of these.
-
+Many JavaScript APIs take an object literal as an argument. For example:
 ```js
 // JavaScript
 printOptions({responsive: true});
 ```
 
+If you want to use `printOptions` from Dart, you cannot simply pass a Dart `Map`
+object – they are are "opaque" in JavaScript.
+
+
+Instead, create a Dart class with both the `@JS()` and
+`@anonymous` annotations.
+
 ```dart
 // Dart
 void main() {
   printOptions(new Options(responsive: true));
 }
 
-@Js()
+@JS()
 external printOptions(Options options);
 
-@Js()
+@JS()
+@anonymous
 class Options {
   external bool get responsive;
 
   external factory Options({bool responsive});
 }
 ```
 
 ## Contributing and Filing Bugs
 
-Please file bugs and features requests on the [Github issue tracker](https://github.com/dart-lang/js-interop/issues).
+Please file bugs and features requests on the [Github issue tracker](https://github.com/dart-lang/sdk/issues).
 
 We also love and accept community contributions, from API suggestions to pull requests.
 Please file an issue before beginning work so we can discuss the design and implementation.
 We are trying to create issues for all current and future work, so if something there intrigues you (or you need it!) join in on the discussion.
 
 Code contributors must sign the
 [Google Individual Contributor License Agreement](https://developers.google.com/open-source/cla/individual?csw=1).