The install instructions tell to add
org.neo4j.server.thirdparty_jaxrs_classes=com.maxdemarzi.processing=/service
to neo4j-server.properties.
However that is not working with Neo4j v3.0.
Instead using
dbms.unmanaged_extension_classes=com.maxdemarzi.processing=/service
is working. I added this to neo4j.conf. Using neo4j-server.properties didn't seem to work.