Refine handling of checkpointing, but still won't work due to SPARK-4196
Prevent exception test from logging a (harmless) stack trace
Update Hadoop, JPMML deps
Integrate app-specific defaults as second reference.conf file. Simplify tests to match. Introduce oryx-ml-oryx-mllib -> oryx-ml-oryx dependency to access reference.conf, and perform now-possible refactorings
Use random HTTP(S) ports for tests
Skip update messages if no model has been seen, rather than fail. Consumers may pick up in mid stream.
Remove unneeded use of MODULE$ from Scala
Closes issue #75 : fix handling of SSL keystore and add tests for security in API