Closed #3332: When the page's visible is false, all sounds should be paused
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-html5 into Iss3332_PauseSounds

Conflicts:
	CocosDenshion/SimpleAudioEngine.js
Merge pull request #1293 from dingpinglv/Iss3332_PauseSounds

Closed #3332: When the page's visible is false, all sounds should be paused