Issue #3943: add a reverse sample function to cc.easeElasticOut
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-html5 into Iss3943_ActionAPI
Merge branch 'Iss3943_ActionAPI' of https://github.com/dingpinglv/cocos2d-html5 into develop-repeat
Issue #3943: Ease reverse