v0.2.1

Fixed

• jml now checks every row up front, before any change, including when core.jml is called
  directly with Executor(apply=True): unknown action, empty username, and movers or leavers that
  don't exist (users created by earlier joiner rows count). Previously a valid row before a bad one
  could already have been applied through the API. All bad lines are reported together.
• The --apply confirmation prompt refuses when stdin is not a terminal and -y isn't passed, so
  piped input such as echo yes | can't confirm a change, and exits 2 (the usage-error code) so cron and CI
  see a failure. Previously only end-of-input counted as no. Declining at an interactive prompt
  still exits 0.