Dockerize npm

[DonRichards]

This adds the ability to build with Docker instead of installing specific versions of Node & gulp directly onto the host machine.

The readme has instructions on how to run it.

---

I wasn't sure if I should add instructions to make this build simpler on isle-dc. This is what I left off of the README. If you find it useful, feel free to add it back.

--- README.md---

Add Custom function to isle-dc to compile quickly

Add the following to custom.Makefile in your isle-dc directory (add the file if it doesn't exist)

# Compile the theme
.PHONY: theme-compile
.SILENT: theme-compile
theme-compile:
	-docker rmi $(docker images | grep 'islandora_theme_build')
	cd $(shell pwd)/codebase/web/themes/contrib/islandora_starter_theme && docker build -t islandora_theme_build .
	docker run --rm -v $(shell pwd)/codebase/web/themes/contrib/islandora_starter_theme:/usr/src/project islandora_theme_build bash -c "bash autobuild.sh"
	docker-compose exec -T drupal bash -lc "drush cc theme-registry"