pkg/shelf: case-insensitive headers, cleaner Request ctor, a lot more tests

pkg/shelf/test/test_util.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 shelf.test_util;
 
 import 'dart:async';
 
 import 'package:shelf/shelf.dart';
 import 'package:shelf/src/util.dart';
@@ skipping 10 matching lines @@
 }
 
 /// Calls [syncHandler] and wraps the response in a [Future].
 Future<Response> asyncHandler(Request request) =>
     new Future(() => syncHandler(request));
 
 /// Makes a simple GET request to [handler] and returns the result.
 Future<Response> makeSimpleRequest(Handler handler) =>
     syncFuture(() => handler(_request));
 
-final _request = new Request('/', '', 'GET', '', '1.1',
-    Uri.parse('http://localhost/'), {});
+final _request = new Request('1.1', 'GET', {}, Uri.parse('http://localhost/'));