Add versioning information for packages and the SDK.

pkg/docgen/lib/src/models/library.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library docgen.models.library;
 
 import 'dart:io';
 
 import 'package:markdown/markdown.dart' as markdown;
 
@@ skipping 124 matching lines @@
 
   String get packagePrefix => packageName == null || packageName.isEmpty ?
       '' : '$packageName/';
 
   Map get previewMap {
     var map = {'packageName': packageName};
     map.addAll(super.previewMap);
     if (packageIntro != null) {
       map['packageIntro'] = packageIntro;
     }
+    var version = packageVersion(mirror);
+    if (version != '' && version != null) map['version'] = version;
     return map;
   }
 
   String get name => docName;
 
   String get docName => getLibraryDocName(mirror);
 
   /// Generates a map describing the [Library] object.
   Map toMap() => {
     'name': name,
@@ skipping 26 matching lines @@
   bool get isPrivate => false;
 
   Indexable get owner => null;
 
   // This is a known incomplete implementation of Indexable
   // overriding noSuchMethod to remove static warnings
   noSuchMethod(Invocation invocation) {
     throw new UnimplementedError(invocation.memberName.toString());
   }
 }