title: Pandas: How to display minor grid lines on x-axis in pd.DataFrame.plot()
body: <p>Is there a way to control grid format when doing pandas.DataFrame.plot()?</p>
  
  <p>Specifically i would like to show the minor gridlines for plotting a DataFrame with a x-axis which has a DateTimeIndex.</p>
  
  <p>Is this possible through the DataFrame.plot()?</p>
  
  <pre><code>df = pd.DataFrame.from_csv(csv_file, parse_dates=True, sep=' ')
  </code></pre>