Prepare for 0.4.0.M1

Docs tweaking and package info renaming in README.md
I still don't understand how the language of this rule communicates clearly what an implementor is supposed to do. Your explanation states "publish safely", which seems obvious, but what does "processing of the respective signals" mean in light of "calls on its `onXXX` methods"?

Forgive me for being so slow on this - but if I don't understand this I an concerned others won't either.