Allow SDK versions <3.0.0 (#32)

And update some dependencies.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3dfbbc6..ce98fe0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.6.8
+
+* Set max SDK version to `<3.0.0`, and adjust other dependencies.
+
 ## 1.6.7+1
 
 * Fix Dart 2 runtime types in `IsolateChannel`.
diff --git a/analysis_options.yaml b/analysis_options.yaml
index bf7c331..d19ee84 100644
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@@ -1,5 +1,4 @@
 analyzer:
-  strong-mode: true
   # These are errors when building in Google
   errors:
     unused_import: error
diff --git a/pubspec.yaml b/pubspec.yaml
index 54bd972..6b1ace3 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,11 +1,15 @@
 name: stream_channel
-version: 1.6.7+1
+version: 1.6.8
+
 description: An abstraction for two-way communication channels.
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/stream_channel
+
 environment:
-  sdk: '>=2.0.0-dev.17.0 <2.0.0'
+  sdk: '>=2.0.0-dev.17.0 <3.0.0'
+
 dependencies:
   async: '>=1.11.0 <3.0.0'
+
 dev_dependencies:
-  test: '^0.12.28'
+  test: ^1.2.0
diff --git a/test/json_document_transformer_test.dart b/test/json_document_transformer_test.dart
index 3c6d11c..6cb97f9 100644
--- a/test/json_document_transformer_test.dart
+++ b/test/json_document_transformer_test.dart
@@ -55,6 +55,6 @@
   test("synchronously throws if an unencodable object is added", () {
     var transformed = channel.transform(jsonDocument);
     expect(() => transformed.sink.add(new Object()),
-        throwsA(new isInstanceOf<JsonUnsupportedObjectError>()));
+        throwsA(new TypeMatcher<JsonUnsupportedObjectError>()));
   });
 }