added support for message_format and notify parameters in send_direct_message method
Added adamcin to AUTHORS
removed mention of 1-on-1 limitations in reply.md
added kwargs support to plugin.py#say() method for 1-on-1 chats
Merge pull request #60 from adamcin/feature/add-message-format-to-private-message

added support for message_format and notify parameters in send_direct_me...