Should fix Pylons/pyramid_mailer#16.
Also completes the fix for #7. I found it was still broken when I did a real local test sending a message with non-ascii address names to a queue.
I hope I did the merging from repoze/master correctly this time.
Recursively cleanup multipart payloads for encoding.
Fix handling of non-ascii strings when queueing messages.
A fix for another problem discovered while working on #9 and
Add coverage for multipart non-ascii messages for #16.
The fix for #16 is in repoze/repoze.sendmail#10.