Elephas IO library does not build

Currently the Elephas modules no longer build due to a bug in the upstream Hadoop libraries related to Guava - HADOOP-11032

Rolling back to 752646c i.e. prior to my merging of the latest Jena master changes the issue does not manifest which means this likely relates to the introduction of Guava as a dependency into Jena since the Hadoop libraries were relying on a really old version of Guava. Looking at mvn dependency:tree this indeed appears to be the case since the managed dependency of Guava in the Jena parent POM overrides the transitive dependency from Hadoop

A temporary workaround may be to override back to the outdated Guava in the elephas POM while awaiting a fix for the Hadoop issue