A simple Dockerfile to add a phantomJS binary directly into
a prebuilt ruby image (for use on those rare occasions
when mounting a Docker volume into an image is not an option...)
The master branch adds /usr/local/bin/phantomjs v2.1.1 into the ruby:2.4.1 prebuilt image.
A docker image is automatically built by DockerHub from this repo and made available at https://hub.docker.com/r/prime8/docker-ruby-phantomjs/