Fixes for zone scanning and signature verification

Hi,

In using the library to validate a huge zone(1mil+ records), I came across a few things that needed to be fixed.  
First, I had to add TYPE66534 recordtype, as zone scanning would die upon finding one.  Secondly, and one that took a long time to track down, is that logic for lowercasing rrdata was changing the original record, and not the one used to compare signatures.  This led to any rrdata with capital letters failing to validate against the rrsig.  From what I could gather, r1 should be the one coerced, and this resolved the issue.

I added my name to contributors in my repo, and hope to contribute more as I run through tests, but am not concerned whether that particular file is accepted considering the small amount of changes.

Thanks!