Prepare for 0.4.0.M1

Docs tweaking and package info renaming in README.md
> You are clearly arguing for the particular design of a specific library here

No, I'm arguing for clarity and flexibility in the spec. Please don't assume intent about "a specific library". I could turn that statement right around. 

Unless we are going to spec out states for a `Publisher` a rule should not suddenly refer to a a specific "shut-down" state. It causes confusion in the spec. It implies a `Publisher` must have state.

Note this wording: "into the `shut-down` state"

That implies that a `Publisher` has a `shut-down` state. Nowhere in the spec is that required or specified or necessary.

Whether a `Subscription` is sharing an underlying resource common to a given `Publisher` is up to the `Publisher` implementation and already covered by the unicast/multicast rules.