Using a module JAR with pre-Project Jigsaw JDK applications

It would be amazing if our modular JARs could be run with pre-Project Jigsaw JDK applications. This way, we will not be concerned with writing another version of our API for pre-JDK 9 applications. The good news is that we can use our modular JARs just as if they were ordinary JARs, that is, JARs without module-info.class at their root. We will see how to do so in this recipe.