2.5.7 missing addSubscriber()

[J-who]

With the latest update, seems that the addSubscriber() method has been removed?
I was using the BackoffPlugin to help deal with #82

[EmilyShepherd]

Probably a side effect of Guzzle changes; the class KeenIOClient used to extend has been split into two. Will have a look if there's a solution to that 😄

[EmilyShepherd]

Hmmm, looks like Guzzle doesn't use the addSubscriber anymore, instead you have to modify the stack with middleware.