title: Coefficient of Variation and NumPy
body: <p>I'd like to create a function with two arguments <code>(a, axis=0)</code> that computes the coefficient of variation of each column or row (2-dimensional array) and returns the index of the column or row with the maximum coefficient of variation.</p>
  
  <p>I understand that <code>.argmax</code>returns the indices of the maximum values along an axis, but I'm unsure of how to proceed after that.</p>
  
  <p>I'd like for the code to pass the following tests:</p>
  
  <pre><code>print(np.asscalar(arg_cvmax(b)) is 2)
  print(np.asscalar(arg_cvmax(b,1)) is 0)
  print(np.asscalar(arg_cvmax(b,axis=1)) is 0)
  </code></pre>