bower update
remove core-popup-menu (now core-dropdown) and update all elements
update pubspec/changelog
updated core_ajax_dart and ported test
update examples
add core-a11y-keys
add core-a11y-keys example
updated changelog
update entry points
update paper_elements dependency
Merge pull request #113 from dart-lang/0.4.1

update to 0.4.1 js versions