Update travis-ci settings (#672)
Update travis-ci settings (#672)

* Remove IRC notifications (nobody lurks in IRC anymore, so this isn't useful)
* Unset _JAVA_OPTIONS to restore default Java options, so plugins don't
  run out of memory and cause the container to get killed
* Remove forking for unit tests; the container doesn't have a lot of CPU
  to fork anyway, and removing this helps with excessive memory utilization
* Use openjdk8
* Use sudo-enabled containers for travis-ci
milleruntime/accumulo,phrocker/accumulo-1,milleruntime/accumulo,lstav/accumulo,milleruntime/accumulo,ctubbsii/accumulo,milleruntime/accumulo,ctubbsii/accumulo,apache/accumulo,lstav/accumulo,keith-turner/accumulo,ctubbsii/accumulo,keith-turner/accumulo,milleruntime/accumulo,apache/accumulo,mjwall/accumulo,phrocker/accumulo-1,keith-turner/accumulo,phrocker/accumulo-1,milleruntime/accumulo,keith-turner/accumulo,ivakegg/accumulo,mjwall/accumulo,apache/accumulo,ctubbsii/accumulo,keith-turner/accumulo,mjwall/accumulo,ivakegg/accumulo,ivakegg/accumulo,phrocker/accumulo-1,milleruntime/accumulo,lstav/accumulo,ivakegg/accumulo,apache/accumulo,ivakegg/accumulo,apache/accumulo,lstav/accumulo,mjwall/accumulo,ctubbsii/accumulo,apache/accumulo,apache/accumulo,phrocker/accumulo-1,keith-turner/accumulo,ctubbsii/accumulo,ctubbsii/accumulo,lstav/accumulo,mjwall/accumulo,phrocker/accumulo-1,ivakegg/accumulo,keith-turner/accumulo,lstav/accumulo,ivakegg/accumulo,mjwall/accumulo,phrocker/accumulo-1,lstav/accumulo,mjwall/accumulo