title: Pandas: can not write to excel file
body: <p>Trying this example from the <a href="http://pandas.pydata.org/pandas-docs/dev/generated/pandas.DataFrame.to_excel.html">documentation</a> </p>
  
  <pre><code>writer = ExcelWriter('output.xlsx')
  df1.to_excel(writer,'Sheet1')
  df2.to_excel(writer,'Sheet2')
  writer.save()
  </code></pre>
  
  <p>I found out that I can not write to an excel file with the error</p>
  
  <pre><code>TypeError: copy() got an unexpected keyword argument 'font'
  </code></pre>
  
  <p>I'm using Panda 0.16 on a Mac pro. </p>
  
  <p>EDIT: 
  writing to an xls file worked just fine. I do not insist in having an xlsx file, just wonder why it does not work.</p>