title: pandas dataframe group and sort by weekday
body: <p>I have pandas DataFrame that includes <code>Day of Week</code> column.</p>
  
  <pre><code>df_weekday = df.groupby(['Day of Week']).sum()
  df_weekday[['Spent', 'Clicks', 'Impressions']].plot(figsize=(16,6), subplots=True);
  </code></pre>
  
  <p>plot the DataFrame displays 'Day of Week' in alphabetical order: <code>'Friday', 'Monday', 'Saturday', 'Sunday' , 'Tuesday' , 'Thursday', 'Wednesday'</code>.</p>
  
  <p>how can i sort and display df_weekday in proper weekday order <code>'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'</code>. ?</p>