'Cancel' for PromiseKit#20

Open

dougzilla32 wants to merge 2 commits intoPromiseKit:masterfrom

cprkit:CoreCancel

Commits on Oct 7, 2018

'Cancel' for PromiseKit -- provides the ability to cancel promises and promise chains
dougzilla32
committed

Commits on Oct 16, 2018

'Cancel' for PromiseKit -- remove cancellable wrappers (they are unnecessary)
dougzilla32
committed