Remove obsolete http_base package

dart/pkg/http_base/test/http_base_io_test.dart

-library http_base.http_base_io_test;
-
-import 'dart:async';
-import 'dart:io';
-import 'dart:convert';
-
-import 'package:http_base/http_base_io.dart';
-import 'package:unittest/unittest.dart';
-
-main() {
-  test('io-client', () {
-    HttpServer.bind('127.0.0.1', 0).then(expectAsync((HttpServer server) {
-      server.first.then(expectAsync((request) {
-        expect(request.method, equals('POST'));
-        expect(request.headers.value('foo'), equals('bar'));
-
-        return request.fold([], (buf, data) => buf..addAll(data)).then((data) {
-          request
-              ..response.statusCode = 201
-              ..response.headers.set('foo', ['foo', 'bar'])
-              ..response.add(data)
-              ..response.close();
-        });
-      })).whenComplete(() => server.close());
-
-      var client = new Client();
-      var uri = Uri.parse('http://127.0.0.1:${server.port}/');
-      var headers = new HeadersImpl({'foo' : 'bar'});
-      var body = (new StreamController()
-          ..add(UTF8.encode('my-data'))
-          ..close()).stream;
-
-      var request = new RequestImpl('POST', uri, headers: headers, body: body);
-      client(request).then(expectAsync((response) {
-        expect(response.statusCode, equals(201));
-        // NOTE: dart:io joins multiple values with ", ".
-        expect(response.headers['foo'], equals('foo, bar'));
-        expect(response.headers.getMultiple('foo').toList(),
-               equals(['foo','bar']));
-
-        response.read()
-            .transform(UTF8.decoder).join('').then(expectAsync((data) {
-          expect(data, equals('my-data'));
-        }));
-      }));
-    }));
-  });
-}