* Require Java 8 and include some Java 8 dependencies.
- Upgrade Jetty to 9.3.16.v20170120.
- Upgrade DataSketches to 0.8.4.
- Bundle caffeine-cache by default.
- Still target Java 7 when compiling base Druid classes.
* Update cluster, quickstart docs.
* Remove oraclejdk7 from travis.yml.
* Enable parallel test
* Remove unnecessary NotThreadSafe annocation
* Randomize the start port when finding available ports
* Fix test failure
* Change to handle all negatives