Prepare for 0.4.0.M1

Docs tweaking and package info renaming in README.md
As per my comments on 1.17 I suggest this needs to be removed or changed. A `Publisher` does not have a "shutdown" state. A `Subscription` does as it is what has the relationship with the `Subscriber` and can be canceled. Canceling a `Subscription` has no influence on the `Publisher` accepting or continuing subscriptions with other `Subscriber`s/`Subscription`s.