title: Convert multiple column dataframe into series
body: <p>I'd like to convert the following into a series.</p>
  
  <pre><code>       Trades Before  Trades After    Predicted    Change
  count   31540.000000   1000.000000  1000.000000 -0.968294
  mean       39.151712     42.216000    90.144811  0.078267
  std       130.948917    143.153156     1.345089  0.093198
  min     -1611.000000  -1371.000000    88.234987 -0.148976
  25%        29.000000     34.000000    89.052902  0.172414
  50%        74.000000     79.000000    89.979200  0.067568
  75%        99.000000    109.000000    91.127657  0.101010
  max       184.000000    179.000000    93.915568 -0.027174
  </code></pre>
  
  <p>Where the index is the combination of the row name and the column name, for example:</p>
  
  <pre><code>Trades After 50%    79.000000    
  </code></pre>