Allow stream_channel version 2.x (#48)

None of the breaking changes impact this package or it's exposed API.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 047ab5b..794f783 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.0.12
+
+* Allow `stream_channel` version 2.x
+
 ## 1.0.11
 
 * Fixed description in pubspec.
diff --git a/pubspec.yaml b/pubspec.yaml
index 1f5b183..f1551c5 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: web_socket_channel
-version: 1.0.11
+version: 1.0.12
 
 description: >-
   StreamChannel wrappers for WebSockets. Provides a cross-platform
@@ -9,12 +9,12 @@
 homepage: https://github.com/dart-lang/web_socket_channel
 
 environment:
-  sdk: '>=2.0.0-dev.23.0 <3.0.0'
+  sdk: ">=2.0.0 <3.0.0"
 
 dependencies:
-  async: '>=1.3.0 <3.0.0'
-  crypto: '>=0.9.2 <3.0.0'
-  stream_channel: ^1.2.0
+  async: ">=1.3.0 <3.0.0"
+  crypto: ">=0.9.2 <3.0.0"
+  stream_channel: ">=1.2.0 <3.0.0"
 
 dev_dependencies:
   pedantic: