Update Default links in Scripting template

@slackmoehrle,

Can you please ask someone to update following links for English

// Learn cc.Class:
//  - [Chinese] http://docs.cocos.com/creator/manual/zh/scripting/class.html
//  - [English] http://www.cocos2d-x.org/docs/creator/en/scripting/class.html
// Learn Attribute:
//  - [Chinese] http://docs.cocos.com/creator/manual/zh/scripting/reference/attributes.html
//  - [English] http://www.cocos2d-x.org/docs/creator/en/scripting/reference/attributes.html
// Learn life-cycle callbacks:
//  - [Chinese] http://docs.cocos.com/creator/manual/zh/scripting/life-cycle-callbacks.html
//  - [English] http://www.cocos2d-x.org/docs/creator/en/scripting/life-cycle-callbacks.html

in default class template in cocos creator?