title: pandas pivot_table keep index
body: <p>i have a dataframe :</p>
  <pre class="lang-py prettyprint-override"><code>import pandas as pd
  
  data = {'day_bucket': ['2011-01-21', '2011-01-22', '2011-01-23', '2011-01-24'], 'label': ['birds', 'birds', 'birds', 'birds'], 'numeric_value': [4, 0, 7, 3]}
  
  df = pd.DataFrame(data)
  
     day_bucket  label  numeric_value
  0  2011-01-21  birds              4
  1  2011-01-22  birds              0
  2  2011-01-23  birds              7
  3  2011-01-24  birds              3
  </code></pre>
  <p>I want to pivot this dataframe so that i have a column <code>birds</code> with the values below it.</p>
  <pre><code>pd.pivot_table(df, values='numeric_value', index='day_bucket',columns='label')  
  </code></pre>
  <p>gives:</p>
  <pre><code>label       birds
  day_bucket             
  2011-01-21  4
  2011-01-22  0
  2011-01-23  7
  2011-01-24  3
  </code></pre>
  <p>what should i do the keep the index? The result will look like:</p>
  <pre><code>    day_bucket birds    
  0   2011-01-21  4
  1   2011-01-22  0
  2   2011-01-23  7
  3   2011-01-24  3 
  </code></pre>