fixed #2293 fixed a bug of cc.LayerColorWebGL that setOpacity is doesn't work.
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-html5 into Iss2293_FixLayerColorBug
Merge pull request #1019 from dingpinglv/Iss2293_FixLayerColorBug

fixed #2293 fixed a bug of cc.LayerColorWebGL that setOpacity is doesn't work