Update version number before publishing.

BUG=

Review URL: https://codereview.chromium.org/1301443005 .
diff --git a/pubspec.yaml b/pubspec.yaml
index 4cc0006..f2c4e06 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: package_config
-version: 0.1.3-dev
+version: 0.1.3
 description: Support for working with Package Resolution config files.
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/package_config