Close the message after operations.

  This updates #124.
  Updated comments.

  Added a couple more close_message() statements.

  Updates #124.
  LInk to the state example.
  Cache the value of ::header(name).

  This provides a speedup, since we've switched to opening
 and closing the underlying file to avoid leaking filehandles
 in #124.
  added.
  Added build-deps
  Include status.
  Include build-status in README.
  Sort files when reading a directory.

  This allows ~/.lumail.d/ and /etc/lumail.d/ to be processed in
 name-based order.
  Don't return a null variable.

  Return "nil" to lua instead.