title: Pivot category column
body: <p>The dataframe</p>
  
  <pre><code>import pandas as pd
  df = pd.DataFrame({'date':['2015-01-01','2015-01-01','2015-01-01','2015-0101','2015-01-02','2015-01-02','2015-01-02','2015-01-02'],
                    'id':[1,1,2,2,1,1,2,2],
                    'kind':['min','max','min','max','min','max','min','max'],
                    'values':[1,2,3,4,5,6,7,8]})
  print(df)
      date        id kind  values
  0  2015-01-01   1  min       1
  1  2015-01-01   1  max       2
  2  2015-01-01   2  min       3
  3  2015-01-01   2  max       4
  4  2015-01-02   1  min       5
  5  2015-01-02   1  max       6
  6  2015-01-02   2  min       7
  7  2015-01-02   2  max       8
  </code></pre>
  
  <p>Contains min and max values for each (unique) combination of date and id.</p>
  
  <p>How can I pivot the <em>kind</em> column, such that the resulting data frame looks like </p>
  
  <pre><code>   date        id min max  
  0  2015-01-01   1  1  2
  1  2015-01-01   2  3  4
  2  2015-01-02   1  5  6
  3  2015-01-02   2  7  8
  </code></pre>
  
  <p>?</p>
  
  <p><code>df.pivot(columns='kind')</code> does not generate the desired result.</p>