Change '127.0.0.1' to 'localhost' to support both IPv4 and IPv6 envs.

BUG=
R=nweiz@google.com

Review-Url: https://codereview.chromium.org//2950883002 .
diff --git a/pubspec.yaml b/pubspec.yaml
index 9beaa7d..1248528 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: http_multi_server
-version: 2.0.3
+version: 2.0.4-dev
 author: "Dart Team <misc@dartlang.org>"
 homepage: http://github.com/dart-lang/http_multi_server
 description:
diff --git a/test/http_multi_server_test.dart b/test/http_multi_server_test.dart
index 9468cfe..d638a48 100644
--- a/test/http_multi_server_test.dart
+++ b/test/http_multi_server_test.dart
@@ -18,9 +18,9 @@
     var subServer3;
     setUp(() {
       return Future.wait([
-        HttpServer.bind("127.0.0.1", 0).then((server) => subServer1 = server),
-        HttpServer.bind("127.0.0.1", 0).then((server) => subServer2 = server),
-        HttpServer.bind("127.0.0.1", 0).then((server) => subServer3 = server)
+        HttpServer.bind("localhost", 0).then((server) => subServer1 = server),
+        HttpServer.bind("localhost", 0).then((server) => subServer2 = server),
+        HttpServer.bind("localhost", 0).then((server) => subServer3 = server)
       ]).then((servers) => multiServer = new HttpMultiServer(servers));
     });
 
@@ -151,7 +151,7 @@
             completion(equals("got request")));
       }
 
-      if (await supportsIPv4) {
+      if (await supportsIPv6) {
         expect(http.read("http://[::1]:${server.port}/"),
             completion(equals("got request")));
       }