TODO

v Fetch users list from Slack API
v Store users list in a file, within the Irssi directory
v When `find_user` is called, if we can't find the users list file, fetch the list
- When `find_user` can't find the requested user, re-fetch the users list
v Add a setting to allow users to set their Slack token
v Calling /swhois without an argument should return information on the current nick
v Notify the user that fetching the users list is going to take a while
v Add in-place help


v2:
v Get presence information on the requested user
v Get the requested user's GitHub URL and Gigster Karma fields (needs users.profile API)

v3:
v Add a command to set/change the current user's profile fields
- Profile field completion (see https://github.com/irssi/scripts.irssi.org/blob/22060fc4669627a9859c92efa2d6651e3673d494/scripts/go.pl)
- Pad colons