Move isolate_channel to it's own import (#39)

Closes #36

This allows the default import to work without triggering any warnings
on the web due to transitively importing `dart:isolate`. This is
required to allow restricting imports based on platform.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 68b68a1..0e125dd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,10 @@
+## 2.0.0
+
+* **Breaking change** `IsolateChannel` requires a separate import
+  `package:stram_channel/isolate_channel.dart`.
+  `package:stream_channel/stream_channel.dart` will now not trigger any platform
+  concerns due to importing `dart:isolate`.
+
 ## 1.7.0
 
 * Make `IsolateChannel` available through
diff --git a/lib/stream_channel.dart b/lib/stream_channel.dart
index a5cd584..e99de08 100644
--- a/lib/stream_channel.dart
+++ b/lib/stream_channel.dart
@@ -12,7 +12,6 @@
 
 export 'src/delegating_stream_channel.dart';
 export 'src/disconnector.dart';
-export 'src/isolate_channel.dart';
 export 'src/json_document_transformer.dart';
 export 'src/multi_channel.dart';
 export 'src/stream_channel_completer.dart';
diff --git a/pubspec.yaml b/pubspec.yaml
index da152fb..917f5bc 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: stream_channel
-version: 1.7.0
+version: 2.0.0
 
 description: An abstraction for two-way communication channels.
 author: Dart Team <misc@dartlang.org>