slack integration

* Ideally not builtin to Cmd, but a separate service
* Using comlab we can incubate in Cmd and split out later
* Not all users in slack would be able to run Cmd.io commands via slack
* They don't have Cmd.io account. Maybe not even Github account.
* Integration form: slash command
* Possible integration scoping
* 1-1 mapping with SSH
* Limited to particular owner / group
* Maybe specific to command
* Slash command webhook URL picks scope
* cmd.io/slack
* cmd.io/slack/gliderlabs
* cmd.io/slack/gliderlabs/deploy
* How to map users, workflow
* Command that gives you a link to authorize both ends and records mapping
* /cmd slack-link
* Knows its the slack user, just needs to auth against Cmd.io (Auth0/github)
* If somehow Cmd.io has token to access Slack API, opens up possiblities
* Put mapping into slack. Signed profile attribute.
* Store everything in Slack as profile fields!
* Global state can be in user profile that setup integration
* How to define permissions? Groups?
* TBD