Make installable as an npm package

[jasonkarns]

Acknowledging that npm is typically thought of as a (and is primarily used for) javascript package manager, it can really be used as a package manager for anything.

npm itself has recognized and encouraged the use of npm (including the registry) as a place to publish non-javascript modules and packages. Indeed, I myself (and the entire nodenv organization),
leverage npm for managing dependencies, versioning, releases, and as a generic script/task runner for the nodenv tools and plugins (which are themselves bash/shell tools and scripts).

Which brings me to my point. The nodenv-package-json-engine nodenv plugin depends on sh-semver (thank you, by the way!).
At present, in order to "update" the sh-semver dependency, we curl down a copy from github and commit it to our repo as a vendored dependency. If sh-semver were to include a package.json manifest (as this PR provides),
then any tools that use npm to manage their dependencies (such as nodenv) would be able to easily list sh-semver as a dependency and allow npm to manage the installation of said dependency.

It is worth noting that, while one is encouraged to actually publish sh-semver to the npm registry, publishing the module is not necessary for others to gain the benefit of it having a package.json manifest (thereby becoming an actual npm package). One can depend on npm packages by pointing to their git repository. Indeed, if it is desired that sh-semver not be published, I would recommend adding "private": true to the package.json manifest to prevent it from accidentally being published at all.

Thoughts?

[jasonkarns]

I just went ahead and made the package private by default. If you end up wanting to publish to npm, just remove the "private": true property from package.json.

Also, if you're not already aware, making this an npm module would add the side benefit of getting a "release" script for free. npm version [major|minor|patch|<version> will bump the version in package.json, commit and tag the release via git all automatically. (Thus eliminating the need to manually bump the VERSION file, commit and tag as I've noticed resulted in at least one weird release: v1.0.0 tag isn't in the master branch.) It is also trivially easy to automate the tests being run before the release process: "preversion": "npm test". Just side benefits to be aware of. :)

[qzb]

Funny, I've originally made this script for choosing node.js version basing on some config files. I guess your nodenv package would be prefect for this :)

I'm already maintaining one shell script in npm - is.sh so I'm aware of benefits. I'll publish it to npm.

[jasonkarns]

Removed private:true

[jasonkarns]

sweet!