Merge pull request #2252 from dingpinglv/Iss5924_ComponentBug

Fixed #5924: fixed a bug of cc.Component that its onExit isn't called.
Issue #5925: Cannot read property 'content' of undefined CCEGLView.js:257
Merge pull request #2253 from VisualSJ/5925

Issue #5925: Cannot read property 'content' of undefined CCEGLView.js:25...
Added fault tolerance to cc.Node for cc.Component.
Merge branch 'develop' of git://github.com/cocos2d/cocos2d-html5 into Iss5924_ComponentBug