title: Getting latest end date in pandas
body: <p>My data has -</p>
  <pre><code>Acc_id  Crt_id  start_date  end_date
  80924   SXD     10/15/11    11/29/11
  80924   HZH     8/15/14     9/28/14
  80924   FYT     2/1/16      1/31/18
  73982   YYU     5/30/11     6/28/11
  15456   26V     5/31/11     5/30/12
  12909   FUY     10/15/17    10/31/19
  80911   TJ5     8/1/11      8/13/11
  75419   KAV     11/1/13     3/4/14
  75419   MNF     11/1/13     12/13/13
  75419   QU3     3/1/14      3/30/14
  </code></pre>
  <p>I need it as-</p>
  <pre><code>Acc_id  Crt_id  start_date  end_date    Acc_end_date
  80924   SXD     10/15/11    11/29/11    1/31/18
  80924   HZH     8/15/14     9/28/14     1/31/18
  80924   FYT     2/1/16      1/31/18     1/31/18
  73982   YYU     5/30/11     6/28/11     6/28/11
  15456   26V     5/31/11     5/30/12     5/30/12
  12909   FUY     10/15/17    10/31/19    10/31/19
  80911   TJ5     8/1/11      8/13/11     8/13/11
  75419   KAV     11/1/13     3/4/14      3/30/14
  75419   MNF     11/1/13     12/13/13    3/30/14
  75419   QU3     3/1/14      3/30/14     3/30/14
  75419   JJK     1/2/12      6/3/12      3/30/14
  </code></pre>
  <p>acc_id end date as the latest crt_id end date in a new column.
  Please advice any approaches, I tried group by and pivot but not not getting anything.</p>