* tests and comments about 'changes' for #291
* add 'changes' tests, improve diagnostic
* preserve trailing newlines in diff output
* use bash trickery to preserve trailing newlines in captured text
* test 'changes' on files without newlines and when called on a non-existant file
* improve comments and variable names
* test with expired key, add 'whoknows -l'
* 'whoknows -l' shows key expiration dates
* also added docs and tests for `whoknows -l`,
* tests for expired keys,
* epoch_to_date functions
* update man pages
* fix epoch-to-date conversion on OSX
* test output of 'whoknows -l'
* fix for lint/shellcheck
* fix for osx
* lint fix
* use date as found in $PATH
* disable 'set -e' as little as possible
* test that hiding secret with expired key fails
* add test of user key without username.
* revert to performing most tests with 'user1'.
* move user4 private/public key fixtures
* factor code fetching emails from keyrings, add comments.
* use factored _warn_or_abort()
* add to, clean up, and clarify comments.
* -F (force even if gpg fails) option for hide and reveal
* allow 'reveal' to decrypt a subset of files.
* update and regen man pages
* man pages update and improvements
* text about why all files should be hidden at once
* add _warn() and _warn_or_abort()
* tests for -F option
* glob source .sh files in Makefile better
* add comment about issue #238. cleanup error msg.
* test exact case in #253
* disable gnupg doc building on ubuntu-rolling
* name keys after emails, not usernames
* use emails to specify users
* rename and add function to get emails from keyrings
* rename directories holding gpg test fixtures
* deny emails that aren't in the keyring, and test.
* require 'killperson' emails to exist in keyring
* change test to reflect killperson must use email
* remove no-longer-needed test function
* factor function _assert_keychain_contains_emais()
* fix/make lint happy
