Prepare for 0.4.0.M1

Docs tweaking and package info renaming in README.md
@benjchristensen You are clearly arguing for the particular design of a specific library here, in general I do not see why we should bake the assumption into the spec that a Publisher is stateless. Allowing it to be stateful does no harm to your use-case, and it is more generic. Therefore I strongly prefer to keep this rule as a suggestion for useful statefulness. Taken together with the removal of 1.15–17 (and then referring to 1.14 in this rule), this should cover all bases.