Add ability to call off without callback

[taylorjdawson]

Use Case:

Users want convenience! Yay western world ideologies! In that vein, make it easy to unsubscribe but allowing the user to forgo the inclusion of the callback when calling off.

Requirements:

• Use the register with the deterministic uuid to locate the event that we want to unsubscribe from

• Then send unsubscribe to the server