Fix casing on dict lookup for PTR records

[BurtBiel]

PTR records were failing to parse for me because the dict lookup for origin returned None. The origin was in fact there, but the dict key was lower-case, not upper-case. I'd love to get this fixed published out so it can be pip installed. Thanks!

[jcnelson]

Hi @BurtBiel, apologies for the late turn-around time (we're gearing up for the next release). Thank you for sending us this PR! We'll test it and merge it into the 0.14 release, which will include the CLI, the server, the core libraries (including this one), and the test framework.

[jcnelson]

Merged to rc-0.14.0. Will be included in the next master.

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