I just found out that a Script I wrote only works on node 0.10 because it uses readable events.

How do I Require a minimum version of node.js in my script so that users know that they need to upgrade?

In package.json:

{ "engines" : { "node" : ">=0.10.3" } }

From the docs.

Edit, a programmatic way:

var pkg = require('./pacakge'),
    semver = require('semver');

if(!semver.satisfies(process.version, pkg.engines.node)) {
  // Not sure if throw or process.exit is best.
  throw new Error('Requires a node version matching ' + pkg.engines.node);
}