Prepare for 0.4.0.M1

Docs tweaking and package info renaming in README.md
I'm for leaving the rule as it as it already links to 1.17 and is self explanatory. I think its rather clever to just prevent leaking publisher resources when no one is interested into its data anymore (it reminds me AMQP auto-delete queue). The Publisher could at least maintain a number of active Subscription (if the implementation doesn't want to have a registry of Subscriptions).
Plus the rule is permissive (SHOULD).