Document how to use JUnitRunner in 3.x

[strowk]

According to documentation latest release is 3.1.0, same documentation explains how to use junit import org.scalatest.junit.JUnitRunner ( http://www.scalatest.org/user_guide/using_junit_runner ), but class org.scalatest.junit.JUnitRunner right now is not present. Documentation should explain how junit could be used in old style and in new style. There should be entry in release notes, saying what has changed and how to migrate to new way.

[tomnis]

hi @strowk maybe you figured it out already, i just ran into this myself and looks like this runner was moved to scalatestplus.junit
https://mvnrepository.com/artifact/org.scalatestplus/junit-4-12_2.12

[Riizade]

https://www.scalatest.org/user_guide/using_junit_runner
https://www.scalatest.org/user_guide/using_the_scalatest_maven_plugin

All official docs still point to the runner being in the old namespace.
This just burned 4+ hours of my time trying to get a new project set up with scalatest + Maven.
The official docs should be updated to indicate that you'll need to specify an additional dependency (org.scalatestplus.JUnit-***)