Add Pub badge (#12)

diff --git a/README.md b/README.md
index 94d3cc7..3687f67 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,4 @@
+[![pub package](https://img.shields.io/pub/v/characters.svg)](https://pub.dev/packages/characters)
 [![Build Status](https://travis-ci.org/dart-lang/characters.svg?branch=master)](https://travis-ci.org/dart-lang/characters)
 
 **NOTE**: This package is considered experimental, and breaking API changes are