title: removing fragment from backstack
body: <p>I want to remove fragment from backstack in the following situations</p>
  
  <ol>
  <li>activity1-->fragment 1-->fragment</li>
  <li>activity1-->fragment 1-->activity2</li>
  </ol>
  
  <p>in both cases on back should return to activity1 skipping fragment1.
  how can i achieve this.code sample would be helpful</p>