Scala: Trees: binary, sorted, tail recursive

Scala: Tail recursive tree traversal
http://www.scala-lang.org/old/node/7984

Scala Tree Sort Examplehttps://www.garysieling.com/blog/scala-tree-sort-example
https://dzone.com/articles/scala-tree-sort-example

Binary tree
http://www.scala-lang.org/old/node/52.html