FR: Better status update functionality

[aph3rson]

Right now, /status is the only way to update a status from slack-cli. However, it'd be nice to use things like expiration times on statuses - this isn't supported in the /status command, but is supported from the API with the users.profile.set method.

This might be nice to integrate in as an option for slack-cli. I could see something along the lines of a new -S flag (vs. -d, etc.), which solely updates a user's status. This could be combined with an optional -e flag for the emoji, and an -x flag for expiration time.