docs: add Node.js requirements

closes #1900

Author: dougwilson

Readme.md

@@ -56,6 +56,15 @@
 
 ## Install
 
+This is a [Node.js](https://nodejs.org/en/) module available through the
+[npm registry](https://www.npmjs.com/).
+
+Before installing, [download and install Node.js](https://nodejs.org/en/download/).
+Node.js 0.6 or higher is required.
+
+Installation is done using the
+[`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally):
+
 ```sh
 $ npm install mysql
 ```