feat: Glip direct messages

[calebbergman]

It appears that currently you're able to send/receive direct messages pertaining to an existing conversation, but you're unable to create a new direct message session with someone; you're only able to create a Team. So if you want to send a message to a single person, you're forced to create a Team, adding them as the only other party to the conversation.

[embbnux]

Thanks @calebbergman It is a good point. Added this feat into backlog.
For now, you can have a direct message when you click user name or avatar in a Glip conversation.