issue #2407: Adds more readability to the class internals for 'ParallaxNode'.
issue #2407: Removing unused codes in Box2dTest.h
issue #2407: Updating SpriteTest.cpp, Don't hide virtual override function.
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into iss2407-class-order
Merge pull request #3174 from dumganhar/iss2407-class-order

issue 2407: Adds more readability to the class internals for 'ParallaxNode'.