* IT: Switch to OpenJDK8 base image.
Also split the Docker image into a base image and a child image, and
build the base image ahead of time for efficiency's sake. Also upgrade
ZK to 3.4.10.
* Additional comments about ZK upgrades.
* 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.
- Make redirects for old links based on _redirects.json
- Replace #{DRUIDVERSION} tokens in docs with current version
- Allow origins named something other than "origin"
- Can use either s3cmd or awscli, depending on availability