Issue #4757: update the CHANGELOG.txt and README.mdown
Merge pull request #1776 from dingpinglv/Iss4757_ReleaseAlpha2

Issue #4757: update the CHANGELOG.txt and README.mdown
 fixed #4853:fix bug cc.winSize incorrect when using setDesignResolutionSize
fix setDesignResolutionSize bug
Merge branch 'develop-3.0' of https://github.com/cocos2d/cocos2d-html5 into develop-3.0

Conflicts:
	cocos2d/core/platform/CCEGLView.js
Fixed #4857: Add check to cc._setup to avoid double invocation
Merge pull request #1778 from joshuastray/develop-3.0

 fixed #4853:fix bug cc.winSize incorrect when using setDesignResolution...
Merge branch 'develop-3.0' of git://github.com/cocos2d/cocos2d-html5 into develop-3.0
Fixed #4670: Null callback check added in Canvas addImage function
Merge pull request #1779 from pandamicro/develop-3.0

Fixed #4857: Add check to cc._setup to avoid double invocation
Closed #4862: Fixed a bug of cc.TMXMapInfo that its tile property id is wrong
Merge branch 'develop-3.0' of https://github.com/cocos2d/cocos2d-html5 into Iss4862_TMXMapInfo
Merge pull request #1780 from dingpinglv/Iss4862_TMXMapInfo

Closed #4862: Fixed a bug of cc.TMXMapInfo that its tile property id is wrong
Merge branch 'develop-3.0' of https://github.com/VisualSJ/cocos2d-html5 into develop-3.0