识别库
https://github.com/goghcrow/capture_easy
生成验证码的库
https://github.com/hanguofeng/gocaptcha
生成图片水印
https://github.com/jianfengye/image-sign
golang的验证码相关的库
原文：http://www.cnblogs.com/ziyouchutuwenwu/p/4946313.html
