Prepare for 0.4.0.M1

Docs tweaking and package info renaming in README.md
Shall that change to Subscription (which implies an active bond between Pub and Sub) :
A `Publisher` MUST produce the same signals in the same sequence for all its `Subscriptions`.   
If a `Publisher` starts with X `Subscriptions` at a given time T, new `Subscribers` attaching to the `Publisher` at a given time T+N MAY NOT receive signals before this period.
A `Publisher` MAY produce the stream elements at (temporarily) differing rates to different `Subscriptions`.