Should it be shouldBeRetried or shouldRetry?

I think we also need to give the user the ability to set the shouldBeRetried option, but also easily get the default behavior if they want.

shouldBeRetried: error => someCondition ? false : defaultBehavior,

Where defaultBehavior is the original !(error instanceof TypeError) || error.isNetworkError check. Not sure the best way to expose this. Could be pRetry.defaultRetryLogic or error.isDefaultRetriable. Or something better?

I like shouldRetry better for the option. What if pRetry exposes a function with the same name as the option, i.e., shouldRetry, to make it concise. The behaviour would be documented anyway.

@stefanpl Friendly bump :)