Log Message:
Update ruby-dnsruby to 1.57.0.

## v1.57.0

* Add query_raw method as alias for send_plain_message, with option to raise or \ 
return error.
* Fixed a bug in RR hash calculation where TTL should have been ignored but wasn't.
* Add support for (obsolete) GPOS resource record type.
* Tweak Travis CI configuration.
* Fix zone reader for case where a line contains whitespace preceding a comment.
* Add post install message.
* Improve README.
* Moved content of NEWS to RELEASE_NOTES.md.
* Use git ls-files now to determine files for inclusion in gem.

## v1.56.0

* Drop support for Ruby 1.8, using lambda -> and hash 'key: value' notations.
* First release since the move from Rubyforge to Github \ 
(https://github.com/alexdalitz/dnsruby).
* Add EDNS client subnet support.
* Relocate CodeMapper subclasses, Resolv, RR, and RRSet classes.
* Add Travis CI and coveralls integration.
* Improve Google IPV6 support.
* Convert some file names to snake case.
* Remove trailing whitespace from lines, and ensure that comments have space \ 
between '#' and text.
* Restore test success when running under JRuby.
* Disabled attempt to connect to Nominet servers, which are no longer available.
* Convert from test/unit to minitest/autorun to support Ruby 2.1+.
* Remove setup.rb.
* Other minor refactoring and improvements to production code, test code, and \ 
documentation.