Merge pull request #1672 from wuzhiming/develop-3.0

add _showNode to node
issue #4221 fixed a bug for layout
Merge branch 'develop-3.0' of https://github.com/cocos2d/cocos2d-html5 into develop-3.0-new
Merge pull request #1673 from xingsenma/develop-3.0

issue #4221 fixed a bug for layout
Issue #4323: update some singleton object's jsDoc
Merge branch 'develop-3.0' of git://github.com/cocos2d/cocos2d-html5 into Iss4323_JsDoc
Merge pull request #1674 from dingpinglv/Iss4323_JsDoc

Issue #4323: update some singleton object's jsDoc
Refactor #3942: Move audioEngine and imeDispatcher initialization into their own file
Merge branch 'develop-3.0' of git://github.com/cocos2d/cocos2d-html5 into SingletonFix
Merge pull request #1675 from pandamicro/SingletonFix

Refactor #3942: Move audioEngine and imeDispatcher initialization into their own file
Remove cc.defineProtoGetterSetter
Merge pull request #1676 from pandamicro/develop-3.0

Remove cc.defineProtoGetterSetter
issue #4277 : Fix a bug of cc.audioEngine.
Merge pull request #1677 from SmallAiTT/iss_4277_fix4release3.0

issue #4277 : Fix a bug of cc.audioEngine.
issue #4277 : Fix a bug of cc.audioEngine : isMusicPlaying.
Merge pull request #1679 from SmallAiTT/iss_4277_fix4release3.0

issue #4277 : Fix a bug of cc.audioEngine : isMusicPlaying.
Issue #4277: add "ie" to multiple audio white list
issue #4277 : Fix a bug of cc.audioEngine : isMusicPlaying.
issue #4277 : Fix a bug of cc.audioEngine : isMusicPlaying.
Merge pull request #1680 from dingpinglv/Iss4277_ReleaseV3.0

Issue #4277: add "ie" to multiple audio white list