title: what is the use case for start(),awaitTermination() and stop() with regard to spark-streaming
body: <p>I am new to spark-streaming.
  I am developing one application that fetches data from terminal and loads into HDFS.
  I searched over the internet but could not understand how to stop streaming application,once it is triggered?</p>
  
  <p>Also would appreciate if you could explain me use case for <code>sc.awaittermination()</code> and <code>sc.stop()</code>.</p>