Merge pull request #2 from cocos2d/master

merge master into fork
fixed mouse scroll event for firefox

fixed scroll event, as firefox uses different events (and delta)
Merge pull request #873 from roed/master

fixed mouse wheel event for firefox
Fixed #1615 Fixed some bugs for Cocos2d-Html5
Merge branch 'master' of https://github.com/cocos2d/cocos2d-html5 into iss1615_WebGLRendering
Merge pull request #876 from dingpinglv/Iss1615_WebGLRendering

Fixed #1615 Fixed some bugs for Cocos2d-Html5