`submysterygift` should trigger follow up `subgift`s

[trezy]

Describe the solution you'd like
Firing a submysterygift should trigger the follow up subgift messages that would be triggered in Twitch. This functionality should be configurable.

Example

submysterygift --count 10
This should trigger the submysterygift response, plus 10 subgift events.

submysterygift --count 10 --no-followup
This should trigger the submysterygift response, but not the subgift events.