show promise usage

README.md

@@ -23,6 +23,21 @@ request('http://www.google.com', function (error, response, body) {
 });
 ```
 
+**Using Promises**
+
+```js
+var promisify = require('util').promisify;
+var request = require('@root/request');
+request = promisify(request);
+
+request('http://www.google.com').then(function (response) {
+  console.log('statusCode:', response && response.statusCode); // Print the response status code if a response was received
+  console.log('body:', response.body); // Print the HTML for the Google homepage.
+}).catch(function (error) {
+  console.log('error:', error); // Print the error if one occurred
+});
+```
+
 ## Table of contents
 
 - [Forms](#forms)