title: Append with date_range() in Python
body: <p>I have a csv file which contains start dates and end dates, with format <code>dd/mm/yy</code>.
  These are read by :</p>
  
  <pre><code>dateparse = lambda x: pnd.datetime.strptime(x, '%d/%m/%y')
  df = pnd.read_csv('file.csv',sep=';',parse_dates=['StartDate','EndDate'], date_parser=dateparse)
  </code></pre>
  
  <p>A sample of the dataframe looks like this:</p>
  
  <pre><code>    StartDate   EndDate
  0   2015-07-15  2015-07-18
  1   2015-06-06  2015-06-08
  </code></pre>
  
  <p>I want to get all the dates listed in these intervals in a column in a new dataframe:</p>
  
  <pre><code>    Date
  0   2015-07-15
  1   2015-07-16
  2   2015-07-17
  3   2015-07-18
  4   2015-06-06  
  5   2015-06-07  
  6   2015-06-08
  </code></pre>
  
  <p>I use iteratively <code>date_range(StartDate, EndDate)</code>, appending each time the result, but I get either an empty array, or something like</p>
  
  <pre><code>[[2015-07-15, 2015-07-16, 2015-07-17, 2015-07-18], [ 2015-06-06, 2015-06-07 , 2015-06-08 ]]
  </code></pre>
  
  <p>and I would like</p>
  
  <pre><code>[ 2015-07-15, 2015-07-16, 2015-07-17, 2015-07-18, 2015-06-06, 2015-06-07 , 2015-06-08 ]
  </code></pre>
  
  <p>What to do?</p>