Fix crash for call runAnimation() in CCBAnimationManagerDelegate::completedAnimationSequenceNamed; Set mRunningSequence to NULL before any runAnimation() call;
Merge branch 'gles20' of https://github.com/tiantian20007/cocos2d-x into pr1757
Updated AUTHORS.
Merge pull request #1870 from dumganhar/pr1757

Fixed a crash for call runAnimation() in CCBAnimationManagerDelegate::completedAnimationSequenceNamed