title: pandas read_csv parse header as string type but i want integer
body: <p>for example, csv file is as below ,(1,2,3) is header!</p>
  
  <pre><code>1,2,3
  0,0,0
  </code></pre>
  
  <p>I read csv file using pd.read_csv and print</p>
  
  <pre><code>import pandas as pd
  df = pd.read_csv('./test.csv')
  print(df[1])
  </code></pre>
  
  <p>it occur error <code>key error:1</code></p>
  
  <p>it seems like that <code>read_csv</code> parse header as string..</p>
  
  <p>is there any way using integer type in dataframe column?</p>