#23 Compile for Java versions pre-Java 9

[Ivan Op de Beeck]

The latest build is apparently compiled to be only compatible with Java 9.
"An Ant BuildException has occured: java.lang.UnsupportedClassVersionError: org/apache/tools/ant/taskdefs/optional/genjar/GenJar has been compiled by a more recent version of the Java Runtime (class file version 53.0), this version of the Java Runtime only recognizes class file versions up to 52.0"
But as far as I can tell, there is no reason for this limitation as the entire project could also be compiled for Java 8 without issue.