title: iOS in-app purchase subscription get free trial period length from SKProduct
body: <p>I am working on in-app purchases with subscriptions.
  In swift, you can get price and price locale from the SKProduct like so:</p>
  
  <pre><code>weeklyProduct.price.doubleValue  
  weeklyProduct.priceLocale.currencySymbol
  </code></pre>
  
  <p>where weeklyProduct is a SKProduct.  </p>
  
  <p>Is it possible to get the free trial length?  For example, I specified a two week free trial for the product.  can I get this from the SKProduct?</p>