Merge pull request #2008 from dingpinglv/Iss5704_CCUIPreformance

Closed #5704: sync Cocos UI and correct some their mistakes
Merge pull request #2011 from VisualSJ/Iss5704_CCUIPreformance

Issue #5704: Fix bug about UISlider
Fixed #5704: Fixed a bug of GUIReader
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-html5 into Iss5704_CCUIPreformance
Issue #5704: Fix bug about UIText