ionic2 - enhancement(events) - Unsubscribe method should be an optional parameter

[zakton5]

Short description of the problem:

Nothing major here, but currently to unsubscribe from a topic you have to write

this.events.unsubscribe('some-topic', null);

This code removes all handlers tied to event 'some-topic'. The null is required.

What behavior are you expecting?

I feel the handler parameter should be optional, yet have the same behavior as is. So I feel like the following code should be valid and still remove all handlers tied to 'some-topic'.

this.events.unsubscribe('some-topic');

[MikeyBeLike]

Agreed