Refactor

Changes

- `[REMOVED]` Built-in clustering
- `[CHANGED]` Response is no longer passed to handlers (just return your result, or if you need to set headers or nack/requeue, `return new Harmonia.Response()`
- `[CHANGED]` Response must be created with `new`. The way it was before was unreliable.
- `[REMOVED]` Dependency on `coyote` (now uses `amqplib` directly)
- `[CHANGED]` Route config (see readme)
- `[ADDED]` Response handler queues (for stateless applications)
- `[ADDED]` When a route receives a header named `x-state`, it will return it to the sender without modification
- `[CHANGED]` Client interface (see readme)

Notes:

- `Client#call` is deprecated (use the alias `Client#awaitMethod` instead).