title: pandas error in dropping column with complex column name
body: <p>For practical reasons I need to define my column name with complex tuples. The problem is that I cannot drop the column as usual as a result. To replicate my problem, </p>
  
  <pre><code>complex_column_name = (u'CHRIS/CME_SP1', 34, ((u'CHRIS/CME_SP1_Settle_rolling_200_mean_to_current_value', 1),))
  
  pd_tmp = pd.DataFrame(np.random.randn(4,1),columns=[complex_column_name])
  
  pd_tmp.drop(complex_column_name,axis=1)
  </code></pre>
  
  <p>The error is :</p>
  
  <pre><code>ValueError: setting an array element with a sequence
  </code></pre>
  
  <p>Any help? Thank you.</p>