* Use trusty for travis jobs.
The distro was set to "precise" in #4572 due to memory issues on trusty,
but we've been seeing performance issues on "precise" recently so let's
see how trusty is working these days.
* Less quiet.
* Adjust memory settings.
* Add back -q option.
* Tweak memory again.
* Adjustments.
* Try squeezing memory a bit more.
* Make Errorprone the default compiler
* Address comments
* Make Error Prone's ClassCanBeStatic rule a error
* Preconditions allow only %s pattern
* Fix DruidCoordinatorBalancerTester
* Try to give the compiler more memory
* Remove distribution module activation on jdk 1.8 because only jdk 1.8 is used now
* Don't show compiler warnings
* Try different travis script
* Fix travis.yml
* Make Error Prone optional again
* For error-prone compiler
* Increase compiler's maxmem
* Don't run Error Prone for benchmarks because of OOM
* Skip install step in Travis
* Remove MetricHolder.writeToChannel()
* In travis.yml, check compilation before tests, because it may fail faster
* 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
Gian Merlino
Jonathan Wei
Jihoon Son
Roman Leventov
Charles Allen
Xavier Léauté