Add request muxer remove jnats

[skunkworker]

Add request muxer similar to Golang's pattern.
Removed JNats. nats-pure gem is fast enough and similar for CRuby and JRuby.
Thread count does not seem to increase with the increased subscriptions.

[film42]

NOTES: from #7

I still don't love this, but I think it's probably fine. We could drop msgs here if ruby performs a long and unhealthy GC between these lines. While not probable, it's possible this happens coming out of a maintenance mode when you're not warm (jruby JITs) and requests are thrashing. But, I don't think there's a clean way to plumb, and it's not worth a thread local context hack...

# Example:

def with_pending_queue(pending_queue:)
  Thread.current[:pending_queue] = @pending_queue 

  yield
ensure
  Thread.current[:pending_queue] = nil
end

module SomethingHorrible
  def initialize
    super 

    @pending_queue = Thread.current[:pending_queue] if Thread.current[:pending_queue].present?
  end
end

class NATS::IO::Subscription
  prepend SomethingHorrible
end

...

with_pending_queue(pending_queue: @pending_queue)
  sub = @nats.subscribe(name, queue: name)

  assert sub.pending_queue == @pending_queue 
end

But... that's pretty nasty 😬

---

But to be honest I think what you're doing is fine because nats is doing a flush on the sub operation so this will probably get hit often.