Update to polymer js version 0.4.1
Update to polymer js version 0.4.1

BUG= http://dartbug.com/21035
R=sigmund@google.com

Review URL: https://codereview.chromium.org//588373003

git-svn-id: dae132d4ca6f88932ad8a9ec3641c81ad1592b72@40631 260f80e4-7a28-3924-810f-c04153c831b5

dart-archive/observe,dart-lang/observe