title: Find the column name which has the maximum value for each row
body: <p>I have a DataFrame like this one:</p>
  
  <pre><code>In [7]:
  frame.head()
  Out[7]:
  Communications and Search   Business    General Lifestyle
  0   0.745763    0.050847    0.118644    0.084746
  0   0.333333    0.000000    0.583333    0.083333
  0   0.617021    0.042553    0.297872    0.042553
  0   0.435897    0.000000    0.410256    0.153846
  0   0.358974    0.076923    0.410256    0.153846
  </code></pre>
  
  <p>In here, I want to ask how to get column name which has maximum value for each row, the desired output is like this:</p>
  
  <pre><code>In [7]:
      frame.head()
      Out[7]:
      Communications and Search   Business    General Lifestyle   Max
      0   0.745763    0.050847    0.118644    0.084746           Communications 
      0   0.333333    0.000000    0.583333    0.083333           Business  
      0   0.617021    0.042553    0.297872    0.042553           Communications 
      0   0.435897    0.000000    0.410256    0.153846           Communications 
      0   0.358974    0.076923    0.410256    0.153846           Business 
  </code></pre>