title: value based conditional selection in pandas throwing ValueError
body: <p>I am trying to select rows from a pandas dataframe based on some condition on one column.
  Let's day, my dataframe columns are: user, age, gender.
  I am trying to figure out rows with user value 'kunal'. I tried two following ways:</p>
  
  <pre><code>df.loc[df.user == 'kunal']
  df.loc[df.user == 'kunal', :]
  </code></pre>
  
  <p>It's throwing the following error:</p>
  
  <pre><code>ValueError: Cannot index with multidimensional key
  </code></pre>
  
  <p>I don't know if pandas has changed anything in the latest version.</p>