Add redex

[yongjhih]

ref. facebook/redex#117

Checklist for Review

NOTE: This checklist is intended for the use of the Official Images maintainers both to track the status of your PR and to help inform you and others of where we're at. As such, please leave the "checking" of items to the repository maintainers. If there is a point below for which you would like to provide additional information or note completion, please do so by commenting on the PR. Thanks! (and thanks for staying patient with us ❤️)

• associated with or contacted upstream?
  • Support Docker facebook/redex#117
• does it fit into one of the common categories? ("service", "language stack", "base distribution")
• is it reasonably popular, or does it solve a particular use case well?
• does a documentation PR exist? (should be reviewed and merged at roughly the same time so that we don't have an empty image page on the Hub for very long)
• dockerization review for best practices and cache gotchas/improvements (ala the official review guidelines)?
• 2+ dockerization review?
• existing official images have been considered as a base? (ie, if foobar needs Node.js, has FROM node:... instead of grabbing node via other means been considered?)
• if FROM scratch, tarballs only exist in a single commit within the associated history?
• passes current tests? any simple new tests that might be appropriate to add? (https://github.com/docker-library/official-images/tree/master/test)

[yongjhih]

• https://travis-ci.org/yongjhih/docker-redex/builds/126153691

Build test of #1674; 658cede (redex):

$ bashbrew build "redex"
Cloning redex (git://github.com/yongjhih/docker-redex) ...
Processing redex:latest ...
$ bashbrew list --uniq "$url" | xargs test/run.sh
testing redex:latest
        'utc' [1/4]...passed
        'cve-2014--shellshock' [2/4]...passed
        'no-hard-coded-passwords' [3/4]...passed
        'override-cmd' [4/4]...passed

[yosifkit]

Sorry for the super long tail. The first step we look for is upstream approval/involvement. It looks like upstream just recommends different users' Dockerfiles (facebook/redex/docs/docker.md and facebook/redex#149) and doesn't want to host them. I'd rather not have us pick and promote one of the images without it coming with approval (and maybe involvement) from upstream redex maintainers. They are welcome to adopt the process of being in Docker official-images, or they can stick with the process they already have.