Delete dartiverse-search from the repo and update dart:io documentation to point

samples/dartiverse_search/lib/github_search_engine.dart

-// Copyright (c) 2013, 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.
-
-part of search_engine;
-
-
-class GithubSearchEngine implements SearchEngine {
-  String get name => 'Github';
-
-  Stream<SearchResult> search(String input) {
-    var query = {
-      'q': 'language:dart $input'
-    };
-    var searchUri = new Uri.https(
-        'api.github.com',
-        '/search/repositories',
-        query);
-    var controller = new StreamController();
-    http_client.get(searchUri)
-      .then((http_client.Response response) {
-        if (response.statusCode != HttpStatus.OK) {
-          throw "Bad status code: ${response.statusCode}, "
-                "message: ${response.reasonPhrase}";
-        }
-        var json = JSON.decode(response.body);
-        json.putIfAbsent('items', () => []);
-        json['items']
-          .expand((item) {
-            if (item['description'] == null ||
-                item['description'].isEmpty) {
-              // Skip results without a description.
-              return [];
-            }
-            return [item];
-          })
-          .take(3)
-          .forEach((item) {
-            controller.add(new SearchResult(
-                item['description'], item['html_url']));
-          });
-      })
-      .catchError(controller.addError)
-      .whenComplete(controller.close);
-    return controller.stream;
-  }
-}