title: Pandas pivot table Percent Calculations
body: <p>Given the following data frame and pivot table:</p>
  <pre><code>import pandas as pd
  df=pd.DataFrame({'A':['x','y','z','x','y','z'],
                   'B':['one','one','one','two','two','two'],
                   'C':[2,18,2,8,2,18]})
  df
  
      A   B       C
  0   x   one     2
  1   y   one     18
  2   z   one     2
  3   x   two     8
  4   y   two     2
  5   z   two     18
  
  table = pd.pivot_table(df, index=['A', 'B'],aggfunc=np.sum)
  
              C
  A   B   
  x   one     2
      two     8
  y   one     18
      two     2
  z   one     2
      two     18
  </code></pre>
  <p>I'd like to add 2 columns to this pivot table; one showing the percent of all values and another for percent within column A like this:</p>
  <pre><code>           C    % of Total  % of B
  A   B
  x   one    2    4%          20%
      two    8    16%         80%
  y   one   18    36%         90%
      two    2    4%          10%
  z   one    2    4%          10%
      two   18    36%         90%
  </code></pre>
  <p>Extra Credit:</p>
  <p>I'd like a bottom summary row which has the sum of column C (it's okay if it also has 100% for the next 2 columns, but nothing is needed for those).</p>