title: How to read csv file as dtype datetime64?
body: <p>Now I have csv file </p>
  
  <pre><code> date
  201605
  201606
  201607
  201608
  </code></pre>
  
  <p>I wanna get dataframe like this</p>
  
  <p>df</p>
  
  <pre><code>      date
  0  2016-05-01
  1  2016-06-01
  2  2016-07-01
  3  2016-08-01
  </code></pre>
  
  <p>so,I would like to read csvfile as datetime64.
  and add the date 1.
  How can I read and transform this csvfile?</p>