Issue #3221: update ChangeLog.txt ,version number and AUTHORS.txt for releasing version v.2.2.1
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-html5 into Iss3221_ReleaseV2.2.1
Issue #3221:  update the CHANGELOG.txt
Merge pull request #1237 from dingpinglv/Iss3221_ReleaseV2.2.1

Issue #3221: update ChangeLog.txt ,version number and AUTHORS.txt for releasing version v.2.2.1