Prepare for 0.4.0.M1

Docs tweaking and package info renaming in README.md
No there isn't. There is a link between the `Subscriber` and `Subscription`. There is no requirement for the `Publisher` to maintain any reference at all to either of those instances after the `Publisher.subscribe` call.

This simple example demonstrates how the `Publisher` is just a factory and never retains a reference to the `Subscriber` or `Subscription`: https://github.com/reactive-streams/reactive-streams/blob/master/api/src/examples/java/org/reactivestreams/example/unicast/InfiniteIncrementNumberPublisher.java
This requirement would force the `Publisher` to maintain a data structure with references to every `Subscriber` that has not yet unsubscribed. That is unnecessary overhead and complexity.