fix code error: add variable winSize's define.

The variable winSize should be defined before used,it's a local variable while not a global variable.

When I used the IDE "JetBrains WebStorm 8.0.3" to debug the tutorial's code both above, I found in the BackgroundLayer.js and StatusLayer.js code , the variable winSize is undefined,so I should first define it through adding "var winSize = cc.Director.getInstance().getWinSize();", the project code provided at last link "https://github.com/chukong/cocos-docs/blob/master/tutorial/framework/html5/parkour-game-with-javascript/chapter4/res/Parkour.zip" is ok while the tutorial's code is not correct!