use reactive-rabbit and newest akka-streams

Quite a lot changes to the API.

For update:
- [x] code
- [ ] comments
- [ ] tutorial
The most popular way of doing this is:

```Scala
import actorSystem.dispatcher
```

From `ActorSystem.class` version 2.3.6:

```Scala
  /**
   * Default dispatcher as configured. This dispatcher is used for all actors
   * in the actor system which do not have a different dispatcher configured
   * explicitly.
   * Importing this member will place the default MessageDispatcher in scope.
   */
  implicit def dispatcher: ExecutionContextExecutor
```