Add CaptchaServer.
Add CaptchaServer.

rainyear/captcha,ZiRo-/captcha,zj8487/captcha,eleme/fork_captcha,dchest/captcha,ZiRo-/captcha,thomasmodeneis/captcha,kaz8/go-captcha,msn217/captcha,gotomypc/captcha,oblank/captcha