Upgrade to Java 8

[ToBeReplaced]

Java 8 has been released for a few months now, and the official Dockerfile should reflect that. Can we update the Dockerfile accordingly and push a new release with tag 8?

[tianon]

Do you know a good place to download OpenJDK 8 binaries? We're currently using the Debian packages for openjdk-7, and packaging for openjdk-8 is still in-progress.

[ToBeReplaced]

openjdk-8 packaging is available in Fedora, if you're comfortable using it.

I use:

FROM fedora:latest
RUN ["yum", "install", "-y", "java-1.8.0-openjdk-headless"]

You could drop the -headless to ship the full runtime environment.