Use Scaladoc for documentation

[eparejatobes]

See

• https://docs.scala-lang.org/style/scaladoc.html
• http://docs.scala-lang.org/overviews/scaladoc/for-library-authors.html
• https://github.com/scala/scala/blob/v2.12.3/test/scaladoc/run/groups.scala

[eparejatobes]

The syntax and basic features are covered here. This is enough as a reference for further doc efforts.

LGTM.