Narrow the SDK constraint to require FutureOr (#89)

Closes #88
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0ab3399..1299d58 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.4.2
+
+* Narrow the SDK constraint to only allow SDK versions that support `FutureOr`.
+
 ## 1.4.1
 
 * Fix the way default values for multi-valued options are printed in argument
diff --git a/pubspec.yaml b/pubspec.yaml
index b733152..91e184e 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: args
-version: 1.4.1
+version: 1.4.2
 author: "Dart Team <misc@dartlang.org>"
 homepage: https://github.com/dart-lang/args
 description: >
@@ -9,4 +9,4 @@
 dev_dependencies:
   test: ">=0.12.0 <0.13.0"
 environment:
-  sdk: ">=1.4.0 <2.0.0"
+  sdk: ">=1.22.0 <2.0.0"