• changed the hashing algorithm used for cache storage from sha256 -> xxh128; the xxHash algorithms are faster
• bugfix: fixed #177 - the "NULL" resource record has an issue because the name conflicts with the PHP reserved word "null", so I
  had originally named it "NUL" instead, but apparently this causes a problem for NTFS in Windows. I've changed it now to be
  "RR_NULL", which is dumb looking, but shouldn't conflict with anything. It can still be created in the way using "NULL", just the
  class name is named inconsistently.
• bugfix: fixed #178 - I was trimming periods from names in the new Data class- which is correct for Domains and Mailboxes, but
  not Text objects, as it can break when you have a domain that happens to line up just right. This fix only trims() the period
  when it's a Domain or Mailbox class.