Added utf8 encode to logger.

when running: afew --move-mails -n

I was getting the error:
Traceback (most recent call last):
  File "/home/chrisfl/.local/bin/afew", line 189, in <module>
    main(options, query_string)
  File "/home/chrisfl/.local/lib/python2.7/site-packages/afew/main.py", line 73, in main
    mover.move(maildir, rules)
  File "/home/chrisfl/.local/lib/python2.7/site-packages/afew/MailMover.py", line 62, in move
    self.__log_move_action(message, maildir, rules[query], self.dry_run)
  File "/home/chrisfl/.local/lib/python2.7/site-packages/afew/MailMover.py", line 103, in __log_move_action
    logging.log(level, "    {}".format(get_message_summary(message)))
UnicodeEncodeError: 'ascii' codec can't encode character u'\xa3' in position 58: ordinal not in range(128)

This fixes it.