issue #2254 : Add plugin weibo for iOS.
fixed #2254 : Add sample code for plugin weibo on iOS.
Update the JS binding code of plugin.
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into develop
Update the license in the sample code.
Merge pull request #2760 from natural-law/develop

Add plugin weibo for iOS on branch develop