title: Do i need to use Consume a Purchase if my app need only one time purchase item?
body: <p>I am using Version 3 API for in App Purchase in my application.
  I am confuse about should i have to call </p>
  
  <pre><code>mHelper.consumeAsync(inventory.getPurchase(SKU_GAS), 
     mConsumeFinishedListener);
  </code></pre>
  
  <p>above method if my application need only one time Purchase of my in app product .</p>
  
  <p>In demo example of In App purchase API 3 they are calling consumeAsync for following listener so why they are calling consumeAsync ?.</p>
  
  <p>1.QueryInventoryFinishedListener when your Product id has purchased.</p>
  
  <p>2.OnIabPurchaseFinishedListener when your product purchase successfully.</p>
  
  <p>Please explain me when to use consumeAyncs method for In app purchase.</p>