Fix incorrect 'domain_record' key

It's almost duplicate of https://github.com/devo-ps/dopy/pull/5
But I get DO TechSupport, and that's what they told me:
> We will update you later with any further findings, however for now, as a programmer-- I would recommend you add a subroutine to accomodate for both of these appearances, just in case.
So, I've added some routine for checking whether the right key exists and fallback if it's not.

By the way, I believe it's critical bug and should be uploaded on PyPi ASAP.