message.rb: make sure [] chunks warning is returned when message is not loaded
test: bad or binary content transfer encodings
test: rename test_messages to test_messages_dir
Revert "Merge #189: Added hidden_alternates config option"

This reverts commit 34287a219b559303fb99cc9b54673171f84702eb.
Merge #204: Revert hidden_alternates option.
Merge branch 'develop' of github.com:sup-heliotrope/sup into develop

re-sync to main dev-line