Replace captcha with ReCaptcha

[llegrand]

Hi,  please consider replacing the current captcha with the recaptcha from Google.   It seems a lot friendlier and much easier on tablets,  phones,  any of the touch screen devices.    I am seeing it used on a lot of sites I access,  like MailChimp etc.

https://www.google.com/recaptcha/intro/index.html

Thanks for at least thinking about it for future release.

Lee