Merge pull request #1767 from dingpinglv/Iss4757_ReleaseAlpha2

Issue #4757: update the version number of Cocos2d-html5 v3.0 alpha2
Fixed #4774: auto full screen switch function added to cc.view
Merge branch 'develop-3.0' of git://github.com/cocos2d/cocos2d-html5 into develop-3.0
Merge pull request #1768 from pandamicro/develop-3.0

Fixed #4774: auto full screen switch function added to cc.view
Issue #4757: update the CHANGELOG.txt and AUTHORS.txt
Merge branch 'develop-3.0' of https://github.com/cocos2d/cocos2d-html5 into Iss4757_ReleaseAlpha2