New, slimmer image and updated Dockerfile

[zwolf]

There were a few issues early this week with PFE deployment Jenkins jobs failing to complete. The issue was node crashing with an error that indicated it was out of memory. Taking a look at the Dockerfile, it seemed that it was building a larger than necessary image (full ubuntu) and loading a bunch of stuff it didn't need (i.e. phantomjs) just to run the npm build.

This PR switches to a slim alpine image straight from npm and only installs git because npm needs it (and bash, but that's probably extraneous). The extra Dockerfile.deps was removed with a piece or two collapsed into the main one. This should keep total image size way down and eliminate the need for two separate images.

This is WIP because while I tested a few docker run commands, I'm not sure how to test short of straight up deploying master to staging and I'd like another pair of PFE-familiar and/or devops eyeballs looking when that happens.

[coveralls]

Coverage increased (+0.6%) to 44.046% when pulling ba0c10a on zwolf:dockerfile-update into e178662 on zooniverse:master.

[srallen]

Phantom.js maybe was needed for the really old build process that used bash scripts. I'm not sure. Regardless, it's a deprecated project and shouldn't be used anymore for that reason alone.

Looks good, but I'm not sure how to test this all exactly either. I'm gonna take a pass at writing some docs on the deployment process to add to the readme in a separate PR.

[rogerhutchings]

We could create another folder in the preview S3 bucket, duplicate the Jenkins job, tweak the stage target folder in package.json and try doing a dry-run deploy to that rather than the original staging folder?

[adammcmaster]

It's a minor thing, but there's no need to update/upgrade here. The --no-cache option loads the package index automatically.

[zwolf]

Good to know. I'm gonna pare this down to just adding git since bash isn't needed and ssh is a dep of git.

[adammcmaster]

It should be safe to just run the normal stage command to test this. docker-compose run dev npm run stage

[zwolf]

Seems to work fine, I was able to successfully stage a branch here with docker-compose run dev npm run stage: https://dockerfile-update.pfe-preview.zooniverse.org/