make CCBAnimationManager::getSequenceId public; add method CCBAnimationManager::getSequenceDuration to get duration of timeline;
Merge pull request #3363 from tiantian20007/localDev

closed 2501: make CCBAnimationManager::getSequenceId public; add method CCBAnimationManager::getSequenceDuration to get duration of timeline;
closed #2501: Update AUTHORS [ci skip]
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into develop