restructured last chapters

chapter15/ch15-node.js

@@ -0,0 +1,11 @@
+const http = require('http');
+
+http.createServer(function(req, res){
+    res.writeHead(200, {'Content-Type': 'text/html'}); //header status code
+    let name = 'maaike';
+    res.write(`Finally, hello ${name}`); //body
+    res.end();
+}).listen(5000); //listen to port 8080
+
+console.log('Listening on port 8080...');
+