title: RxAndroid - save data when activity is destroyed
body: <p>Consider this scenario:</p>
  
  <ul>
  <li>Perform computational heavy task at Activity1 (assume it takes 20 seconds)</li>
  <li>User killed Activity1 at 10th second</li>
  <li>When task gets completed, save the data in Database. (UI updation not required)</li>
  </ul>
  
  <p>Now, since <code>subscription.unsubscribe();</code> gets called on <code>OnDestory();</code>, I was unable to save the data in Database.</p>
  
  <p><strong>Question:</strong>
  What is the best pattern, so that there shouldn't be data loss after tasks get completed?</p>