Prepare for 0.4.0.M1

Docs tweaking and package info renaming in README.md
`Publisher.subscribe` SHOULD NOT throw a non-fatal  `Throwable`. The only legal way to signal failure (or reject a `Subscription`) is via the `onError` method. Non-fatal `Throwable` excludes any non-recoverable  exception by the application (e.g. OutOfMemory) |