tea： 二维码又称#QR Code# ，QR全称Quick Response，是一个近几年来移动设备上超流行的一种编码方式，它比传统的Bar Code条形码能存更多的信息，也能表示更多的数据类型，比如：字符，数字，日文，中文等等。
Limitations and Cautions
o The QR specification includes modes for encoding numeric, alphanumeric, or
Kanji data more efficiently. This package does not (yet) offer those options.
o The QR specification offers ways to string lengthy data across multiple QR
codes. This package does not implement that possibility.