Neopets.com recently added some new security rules that, if not
satisfied, cause the request to return 403 Forbidden.
We figured these out through trial and error, and added them to the
`DTIRequests` library, so they would apply to all requests we make.
We also updated our AMFPHP library to use `DTIRequests` as well, as an
easy way to get the same security rules to apply to those requests.
This change was motivated by pet loading being down for the past day or
so, because all pet loading requests were returning 403 Forbidden! Now,
we've fixed it, hooray!
Just a wrapper for the barrier/semaphore thing we're doing constantly!
I only applied it in the importer rake tasks for now. There's other
call sites to move over to it, too!
