Update pubspec.yaml

Description fix.
diff --git a/pubspec.yaml b/pubspec.yaml
index 70ede94..9952d7a 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,7 +1,7 @@
 name: cli_util
 version: 0.0.1
 author: Dart Team <misc@dartlang.org>
-description: A utility to help in building Dart command-line apps.
+description: A library to help in building Dart command-line apps.
 homepage: https://github.com/dart-lang/cli_util
 environment:
   sdk: '>=1.0.0 <2.0.0'