IntelliJ IDEA 14.x How To Resolve "routes" Activator/Play Object

Problem:

You just imported the SBT project of Activator or Play framework app in IntelliJ IDEA (14), and you found that you "routes" among other symbols do not resolve.

Root Cause:

You are lacking the dependency for the auto-generated routing class.

Solution:

You can add Module Dependency to classes_managed. This is located in the target/scala_2.xx/classes_managed

I originally posted a similar solution, but this one is much better and works with Play 2.3 or later. This video shows you exactly what you will need to do.