Bump version number to publish. (#58)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0c20ba4..9c965fa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,4 @@
-## 0.21.1-dev
+## 0.21.1
 
 * Updated one test to comply with Dart 2 voidness semantics.
 * Fix Dart 2 runtime cast failure in `toObservable()`.
diff --git a/pubspec.yaml b/pubspec.yaml
index f64bcdc..cbe0f38 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: observable
-version: 0.21.1-dev
+version: 0.21.1
 author: Dart Team <misc@dartlang.org>
 description: Support for marking objects as observable
 homepage: https://github.com/dart-lang/observable