Update changelog and version to 1.20 for release to CPAN.

Ignore common temp files in repo.

Bump to 1.19 for release to CPAN

Bump to 1.18 for release to CPAN

Version 1.17

Release 1.16

Release 1.15.

Release 1.14.

Release 1.12.

Support SHA-224.

Tweak.