Don’t find node_modules up the directory tree when installing

[lydell]

elm-tooling install creates links in node_modules/.bin/.

Currently, it looks up the directory tree (starting from the directory containing elm-tooling.json) and errors out if no node_modules is found.

This is “unsound”. Consider this directory structure:

project/
	package.json
	node_modules/
	appA/
		elm.json
		elm-tooling.json
		src/
	appB/
		elm.json
		elm-tooling.json
		src/

What should project/node_modules/.bin/elm link to? appA’s Elm version or appB’s Elm version?

Besides, elm-tooling.json only affects the current project. So elm-tooling install shouldn’t touch stuff outside the project.

This PR fixes the node_modules locator. Now, elm-tooling install does the only correct thing – installs into node_modules in the same directory as elm-tooling.json. If node_modules doesn’t exist it is created.

Note: This has an interesting secondary effect. Yarn 2 does not create a local node_modules folder. So if you install elm-tooling using Yarn 2, you’ll now get a local node_modules folder. It will only contain a .bin/ folder with links to your tools. This should be fine, and even wanted. Editors support node_modules/.bin/ out of the box. In other words, it should now be possible to use elm-tooling with Yarn 2 without getting errors.