A Simple Publish/Subscribe Example in Scala

Here is an example where using a simple publish/subscribe mechanism allowed me to clean up some of my early Scala code. My Mimprint program (now also on github) was originally written in Java, then ported to Scala soon after I first started learning that language. As such, much of that original ported code was "Java written in Scala". As I have continued to internalize the Scala approach I have go