Merge pull request #2054 from dingpinglv/Iss5704_FixUIBug

Fixed #5704: fixed a bug of ccui.Layout
Fixed #5704: fixed a bug of WidgetReader that it gets a incorrect value when color's value is 0
Merge branch 'develop' of git://github.com/cocos2d/cocos2d-html5 into Iss5704_FixUIBug