101 Fix scaladoc warnings - fixed in streaming but leaving the rest as i...

...s. This is a known bug that will be fixed in a later version of Scala. Minor cleanup of build and addition of sbt unidoc plugin
Can we use [this](http://www.scala-sbt.org/0.13/docs/Howto-Scaladoc.html#Enable+automatic+linking+to+the+external+Scaladoc+of+managed+dependencies) to automatically link the documentation to external projects?