Enable adoption in modularized Java 9 projects

[nictas]

Currently, this project can't be used in a modularized Java 9 (or greater) project, because it cannot be required as a module:

module foo {

    requires org.apache.commons.collections4;
    requires com.vdurmont.semver4j; // Does not compile!

}

The easiest way to solve this is to add an automatic module name as I've done in this PR. There's also another way that involves the creation of a module-info.java file, but it also requires the adoption of Java 9 in this project, which is unwise IMO.

More info here: https://blog.joda.org/2018/03/jpms-negative-benefits.html

[piotrooo]

This will be fixed in 2.1.0 in active copy of this lib: https://github.com/semver4j/semver4j