title: Stripe - Additional Invoice Item included on recurring payment
body: <p>I am having a problem adding invoice item on subscription and currently banging my head on the wall.</p>
  <p>I've created an Invoice Item on stripe and I’d like the Invoice Item to be included on the recurring payment</p>
  <p>Here’s my code, it adds an invoice item on first invoice but not on the next invoice.</p>
  <pre><code>$new_customer = Stripe_Customer::create(array(
      'card' =&gt; $card,
      'email' =&gt; $email,)
  );
  Stripe_InvoiceItem::create(array(
      'customer' =&gt; $new_customer['id'],
      'amount' =&gt; $additiona_charges,
      'currency' =&gt; 'gbp',
      'description' =&gt; 'Addtional Cities'
  ));
  $new_customer-&gt;updateSubscription(array('plan' =&gt; $selected_plan, 'prorate' =&gt; true));
  </code></pre>
  <p>On my current set-up. I have additional custom charges based on customer selection upon subscription thats way I need to add additional charges on recurring payment.</p>
  <p>Its something like this</p>
  <h2>Plan</h2>
  <pre><code>1 Cookie - 99GBP  / Per month
  2 Cookies - 199GBP / Per month
  3 Cookies - 300GBP / Per month
  </code></pre>
  <h2>Additional Charges - Invoice Items</h2>
  <pre><code>-With Candle - +20GBP // must be included on recurring payment.
  -With Icecream - +26GBP // must be included on recurring payment.
  -With Cheese - +28GBP // must be included on recurring payment.
  -With Ketchup - +30 //  must be included on recurring payment.
  -With Poison (for your X) -  +50 //  must be included on recurring payment.
  </code></pre>
  <p>I hope someone could help. Thanks so much</p>
  <p>Cheers
  Kenn</p>