Release 1.3.4 (#22)

diff --git a/pubspec.yaml b/pubspec.yaml
index eac5cb0..7f6dd0c 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: pub_semver
-version: 1.3.3
+version: 1.3.4
 author: Dart Team <misc@dartlang.org>
 description: >
  Versions and version constraints implementing pub's versioning policy. This