gem ‘cocoon‘ - javascript "cocoon.js" https://note.youdao.com/web/#/file/XCiivnE/note/WEB44679b433b54ea9a6fc908b5a7cfa2e7/?search=%E4%B8%80%E5%AF%B9%E5%A4%9A
一对多 添加表单 cocoon
原文：http://www.cnblogs.com/znsongshu/p/6080161.html
