Migration to v0.7

As can be seen there are several rough edges. More boilerplate for simple flows, e.g. the foreach-oncomplete.

The tutorial documentation is not updated yet.
yes, that is more compact
I kind of miss foreach convenience:

    val completedFuture =  FlowFrom(text.split("\\s").toVector)
      .map(_.toUpperCase)
      .foreach(println)