Added simple prepublish script, preventing publications with npm lowe…

…r than 4 (which introduced support for prepare script)

package.json

@@ -38,6 +38,7 @@
     "test:karma": "karma start test/karma.conf.js --single-run",
     "test:nodom": "mocha test/no-dom-test.js",
     "precommit": "npm test && lint-staged",
+    "prepublish": "test $(npm -v | tr . '\n' | head -n 1) -ge '4' || exit 1",
     "prepare": "npm run build"
   },
   "devDependencies": {