bower update
add core_popup_menu to config and run update tool
add core_popup_overlay
user Content-Type instead of content-type
update/fix all examples
remove platform.js from all examples :)
remove platform.js from all tests
update pubspec and changelog
code review updates
widen paper elements constraing
Merge pull request #102 from jakemac53/0.4.0

update to 0.4.0 js versions