title: RxAndroid: Create an observable which make a request and returns success/error based on response
body: <p>I would like to create an Observable based on the following scenario:</p>
  
  <ol>
  <li>A request is made to the server</li>
  <li>The response then added to cache. </li>
  <li>If adding to cache is successfully only then is the success response emitted to the observer. </li>
  </ol>
  
  <p>Thanks.</p>