Clean up internal uses of concat (dart-lang/stream_transform#44)

pkgs/stream_transform/lib/src/start_with.dart

diff --git a/pkgs/stream_transform/lib/src/start_with.dart b/pkgs/stream_transform/lib/src/start_with.dart
index a98eb6d..9434748 100644
--- a/pkgs/stream_transform/lib/src/start_with.dart
+++ b/pkgs/stream_transform/lib/src/start_with.dart
@@ -5,7 +5,7 @@
 import 'dart:async';
 
 import 'bind.dart';
-import 'concat.dart';
+import 'followed_by.dart';
 
 /// Emits [initial] before any values from the original stream.
 ///
@@ -31,5 +31,5 @@
       if (values.isBroadcast && !initial.isBroadcast) {
         initial = initial.asBroadcastStream();
       }
-      return initial.transform(concat(values));
+      return initial.transform(followedBy(values));
     });

pkgs/stream_transform/test/followd_by_test.dart

diff --git a/pkgs/stream_transform/test/followd_by_test.dart b/pkgs/stream_transform/test/followd_by_test.dart
index 37a46f7..2bff18c 100644
--- a/pkgs/stream_transform/test/followd_by_test.dart
+++ b/pkgs/stream_transform/test/followd_by_test.dart
@@ -14,7 +14,7 @@
   };
   for (var firstType in streamTypes.keys) {
     for (var secondType in streamTypes.keys) {
-      group('concat [$firstType] with [$secondType]', () {
+      group('followedBy [$firstType] with [$secondType]', () {
         StreamController first;
         StreamController second;
 
@@ -45,7 +45,7 @@
           emittedValues = [];
           errors = [];
           isDone = false;
-          transformed = first.stream.transform(concat(second.stream));
+          transformed = first.stream.transform(followedBy(second.stream));
           subscription = transformed
               .listen(emittedValues.add, onError: errors.add, onDone: () {
             isDone = true;