Add user command

This command will be used to:

1. Find user details
2. Block users
3. Unblock users
4. Gather events (https://gitlab.com/gitlab-cog/gitlab-admin/blob/master/lib/cog_cmd/gitlab/user/events.rb)
5. Grabbing the last event (https://gitlab.com/gitlab-cog/gitlab-admin/blob/master/lib/cog_cmd/gitlab/user/lastevent.rb)
6. Updating user Email (https://gitlab.com/gitlab-cog/gitlab-admin/blob/master/lib/cog_cmd/gitlab/user/email/update.rb), if we actually need this (seems like a bit of a weird command to have)