title: Calculate distance between latitude and longitude in dataframe
body: <p>I have 4 columns in my dataframe containing the following data: <br></p>
  <pre><code>Start_latitude&lt;br&gt;
  Start_longitude&lt;br&gt;
  Stop_latitude&lt;br&gt;
  Stop_longitude&lt;br&gt;
  </code></pre>
  <p>I need to compute distance between the latitude longitude pair and create a new column with the distance computed.</p>
  <p>I came across a package (geopy) which can do this for me. But I need to pass a tuple to geopy. How do i apply this function (geopy) across the dataframe in pandas for all the records?</p>