improve preinstall script

build/npm/preinstall.js

@@ -3,8 +3,21 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
+let err = false;
+
+const major = parseInt(/^(\d+)\./.exec(process.versions.node)[1]);
+
+if (major < 8) {
+	console.error('\033[1;31m*** Please use node>=8.\033[0;0m');
+	err = true;
+}
+
 if (!/yarn\.js$/.test(process.env['npm_execpath'])) {
-	console.error('*** Please use yarn to install dependencies.\n');
+	console.error('\033[1;31m*** Please use yarn to install dependencies.\033[0;0m');
+	err = true;
+}
 
+if (err) {
+	console.error('');
 	process.exit(1);
-}
+}
\ No newline at end of file

package.json

@@ -127,4 +127,4 @@
     "windows-mutex": "^0.2.0",
     "windows-process-tree": "0.1.6"
   }
-}
+}
\ No newline at end of file