Update CCEditBoxImplIOS.mm

https://github.com/sunxiaoyu/cocos2d-x/commit/02c664730669c7e3d5d0ecc727deab9aa785c2c7
Update AUTHORS [ci skip]
Merge pull request #2748 from dumganhar/iss2253-refactor-editbox-master

fixed #2253: [CCEditBox iOS] Adding UITextField only when keyboard was opened, removing it when keyboard was closed.