Add unsafeRunToTwitterFuture for twitter Future

[yaroot]

Allow evaluating ZIO to twitter Future. Unfortunately the only place I could add this method is the Runtime[R] because it needs to evaluate Fiber.interrupt when being cancelled

[jdegoes]

Looks good! Just a couple minor comments on efficiency.

[jdegoes]

Which test is the flaky one? Happy to help you with it!

[yaroot]

propagateInterrupts fail most of the time, basically fiber.interrupt should cancel the underlying future but it doesn't, making the whole thing fail.

https://github.com/scalaz/scalaz-zio/blob/d64faa87c154b522a767568831b6f8cab6468a50/interop-twitter/jvm/src/test/scala/scalaz/zio/interop/TwitterSpec.scala#L50-L57

[jdegoes]

@yaroot

The logic is not very simple, but it's possible fromTwitterFuture is not propagating the interruption signal.

This would be a more logical implementation to me:

    final def fromTwitterFuture[A](future: Task[Future[A]]): Task[A] =
      Task.uninterruptibleMask(restore =>
        future.flatMap { f =>
          restore(Task.effectAsync { cb =>
            f.respond {
              case Return(a) => cb(Task.succeed(a))
              case Throw(e)  => cb(Task.fail(e))
            }
          }).onInterrupt(UIO(f.raise(new FutureCancelledException)))
        )
      }

[yaroot]

@jdegoes ah yes, I println debugged it, the promise interruption handler was never called.

[yaroot]

@jdegoes could you take another look?

[jdegoes]

Looks good to me. Thank you for your work on this!

[jdegoes]

Congratulations on your first ZIO pull request, and thank you for the contribution!