title: Resampling a pandas DataFrame by business days gives bad results
body: <p>When I run the following code, the results appear to add the non-business day data to the result.</p>
  
  <p><strong>Code</strong></p>
  
  <pre><code>import pandas as pd
  
  df = pd.DataFrame({'id': [30820864, 32295510, 30913444, 30913445],
                     'ticket_id': [100, 101, 102, 103],
                     'date_time': [
                         '6/1/17 9:48',
                         '6/2/17 13:11',
                         '6/3/17 13:15',
                         '6/5/17 13:15'],
                     })
  df['date_time'] = pd.to_datetime(df['date_time'])
  df.index = df['date_time']
  
  x = df.resample('B').count()
  print(x)
  </code></pre>
  
  <p><strong>Result</strong></p>
  
  <pre><code>            id  ticket_id  date_time  
  date_time                                     
  2017-06-01   1          0          1 
  2017-06-02   2          0          2 
  2017-06-05   1          0          1 
  </code></pre>
  
  <p>I would expect that the count for 2017-06-02 would be 1 and not 2. Shouldn't the data from a non-business day (6/3/17) be ignored? </p>