Add JavaScript code example (#35)

* Add JavaScript code example

* Update snippet to working version

README.md

@@ -1,16 +1,16 @@
 # CH-Payments
 Welcome to CH Payments, a simple paymentprovider wrapper for stuff you want CH to get money for.
 Payments makes it easy to create products, and implement it in your own website.
-No hassle with keys, accounts and webhooks, just a single call to initiate a payment. 
+No hassle with keys, accounts and webhooks, just a single call to initiate a payment.
 
 Below you can find some ready-to-use code examples for your website.
 
-The administration panel (for now) is only available for board members. 
+The administration panel (for now) is only available for board members.
 They can create products to generate the keys required.
 
 # Code examples
-No idea how to code, but still want to sell tickets on your CH site? 
-Use one of these code examples to get going. 
+No idea how to code, but still want to sell tickets on your CH site?
+Use one of these code examples to get going.
 
 #### Python 3.5
 ```python
@@ -31,23 +31,53 @@ print(response.json())
 ```
 
 #### JavaScript
-[Code example required](https://github.com/WISVCH/payments/issues/6)
+
+The full workflow is as follows.
+
+```js
+async function main() {
+  const productsRequest = await fetch('http://localhost:9000/api/products/SYMPOSIUM/2016');
+  const products = await productsRequest.json();
+
+  const orderRequest = await fetch('http://localhost:9000/api/orders', {
+    method: 'POST',
+    headers: {'Content-Type':'application/json'},
+    body: JSON.stringify({
+      name: 'Thomas Ticket',
+      email: '[email protected]',
+      returnUrl: 'https://www.ch.tudelft.nl/payments/ordercompleted',
+      productKeys: products.map(p => p.key)
+    })
+  });
+  const order = await orderRequest.json();
+  console.log(`You should redirect the user to url ${order.url}`);
+
+  // After that you can obtain the order status with:
+  const statusRequest = await fetch(`http://localhost:9000/api/orders/${order.publicReference}`);
+  const status = await statusRequest.json();
+  console.log(`The order status is right now ${status.status}`);
+}
+
+main();
+```
+
+(You can copy-paste this snippet into the Dev console of your browser to try it out. It requires Chrome 55+.
 
 #### PHP
 [Code example required](https://github.com/WISVCH/payments/issues/6)
 
 # HootHub
 This project currently is quite minimal, and offers lots of opportunities for great features built by you!
-Check out the issue page for HootHub issues, and start earning Uilenballen. 
+Check out the issue page for HootHub issues, and start earning Uilenballen.
 
 First, pick an issue and self-assign it. Make your changes in a new branch, with the following naming convention:
 
 - Fixing a bug? > "fix-description_of_bug"
 - Implementing a new feature? > "feature-description_of_feature"
 
-Once you're satisfied with your changes, create a pull request and give it the label "Ready for review". 
-You can assign someone in specific or wait for someone to pick it up. 
-Make sure to include tests and documentation. 
+Once you're satisfied with your changes, create a pull request and give it the label "Ready for review".
+You can assign someone in specific or wait for someone to pick it up.
+Make sure to include tests and documentation.
 If Travis isn't happy, we're not happy.
 
 # Running