title: Find end date of quarter given date, pandas
body: <p>Assume we have a table like</p>
  
  <pre><code>table = [[datetime.datetime(2015, 1, 1), 1, 0.5],
           [datetime.datetime(2015, 1, 27), 1, 0.5],
           [datetime.datetime(2015, 1, 31), 1, 0.5],
           [datetime.datetime(2015, 2, 1), 1, 2],
           [datetime.datetime(2015, 2, 3), 1, 2],
           [datetime.datetime(2015, 2, 15), 1, 2],
           [datetime.datetime(2015, 2, 28), 1, 2],
           [datetime.datetime(2015, 3, 1), 1, 3],
           [datetime.datetime(2015, 3, 17), 1, 3],
           [datetime.datetime(2015, 3, 31), 1, 3]]
  
  df = pd.DataFrame(table, columns=['Date', 'Id', 'Value'])
  </code></pre>
  
  <p>Is there a way to get the specific end date of the <em>actual</em> quarter given the dates in the column <code>Date</code>? E.g., I would like to add the column <code>Q_date</code> to <code>df</code> such that</p>
  
  <pre><code>        Date  Id  Value  Qdate
  0 2015-01-01   1    0.5  2015-03-31
  1 2015-01-27   1    0.5  2015-03-31
  2 2015-01-31   1    0.5  2015-03-31
  3 2015-02-01   1    2.0  2015-03-31
  4 2015-02-03   1    2.0  2015-03-31
  5 2015-02-15   1    2.0  2015-03-31
  6 2015-02-28   1    2.0  2015-03-31
  7 2015-03-01   1    3.0  2015-03-31
  8 2015-03-17   1    3.0  2015-03-31
  9 2015-03-31   1    3.0  2015-03-31
  </code></pre>
  
  <p>I've only considered the first quarter for simplicity - as I know what date it is.</p>