版本：
文件：
- https://cdn.bootcdn.net/ajax/libs/p2.js/0.7.1/p2.js
- https://cdn.bootcdn.net/ajax/libs/p2.js/0.7.1/p2.min.js
- https://cdn.bootcdn.net/ajax/libs/p2.js/0.7.1/p2.renderer.js
- https://cdn.bootcdn.net/ajax/libs/p2.js/0.7.1/p2.renderer.min.js