* updated fixture key for user3, fixes#607
* update tests/fixtures/gpg/README.md
* mention fix of #607 and #609 in changelog
* use shellcheck 0.7.1, not 'latest' for #609
* 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