Update node version

             @@ -12,7 +12,7 @@    12     12npm install eshttp    13     13```    14     14    15       Requires ES6/2015 JS engine (Node.js 4.0). Example web server using eshttp:           15Requires ES6/2015 JS engine (Node.js 18.0). Example web server using eshttp:    16     16    17     17```js    18     18'use strict';