v1.1.0

• Add optional rasuvaeff/duration integration. Purely additive: the existing
  millisecond int API is unchanged and fully backwards-compatible.
• Duration-typed factories alongside the int-ms ones: Retry::fixedFor(),
  Retry::exponentialFor(), Retry::withFixedFor(),
  Retry::withExponentialFor(), Retry::stopAfter(), plus
  RetryPolicy::fixedFor() and RetryPolicy::exponentialFor().
• AttemptRecord::delay(): ?Duration and AttemptRecord::elapsed(): Duration
  (and the same on Http\HttpAttemptRecord) expose the millisecond fields as
  Duration value objects.