[Feature] Add check for Domain Name Validation

[kohenkatz]

ReCaptcha has a new feature (replacing the old "Secure Token" feature) called Domain Name Validation. The way it works is that reCaptcha sends you the domain name on which the captcha was filled out when it tells you whether the captcha was filled successfully or not. The idea is that you can check to make sure that the domain it was filled out on is one that you have allowed.

This is very handy for those of us who use reCaptcha on a large number of domains (or with a list of domains that changes often) and have turned off the built-in Domain Name Validation in the reCaptcha admin console.

If you are interested in accepting a Pull Request for this feature, I would be happy to provide one, but I want to see whether you are interested before I do the work.

Thanks!

[anhskohbo]

Any pull request pls?

[kohenkatz]

I'll put together a Pull Request next week.