title: StratifiedKFold in python giving error
body: <p>in python I am importing </p>
  
  <pre><code>&gt;&gt;&gt; from sklearn.model_selection import StratifiedKFold
  
  &gt;&gt;&gt; cv = StratifiedKFold(y, n_folds=5)
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  TypeError: __init__() got an unexpected keyword argument 'n_folds'
  
  &gt;&gt;&gt; print('The sklearn version is {}.'.format(sklearn.__version__))
  The sklearn version is 0.18.1.
  </code></pre>
  
  <p>I have sklearn 0.18.1. Any idea why i m getting this error?</p>