title: Resample time series data hourly with gaps
body: <p>I have a year-long data set with dates and temperatures that's sample every 15min with occasional gaps in the data in Python. I've saved the dates and temperatures into a dataframe in pandas: </p>
  
  <pre><code>2015-08-21 09:35:47  27.928
  2015-08-21 09:55:47  28.839
  2015-08-21 10:15:47  28.495
  ...
  2016-08-10 05:39:24  11.246
  2016-08-10 05:59:24  11.912
  2016-08-10 06:19:24  13.066
  </code></pre>
  
  <p>I would like to resample the data into every hour and tried with this line:</p>
  
  <pre><code> newDat=data.resample(rule='H')
  </code></pre>
  
  <p>I also tried using the first and last 'how' but still didn't get what I was looking for. My results looked like:</p>
  
  <pre><code>2015-08-21 09:00:00  28.383500
  2015-08-21 10:00:00  27.959667
  2015-08-21 11:00:00  29.513333
  ...
  2016-08-10 06:00:00  14.235667
  2016-08-10 07:00:00  20.867333
  2016-08-10 08:00:00  26.725000
  </code></pre>
  
  <p>I don't want the actual temperature or time values changed. I would like the command to grab the first times within every hour of the day so I get something  like:</p>
  
  <pre><code>2015-08-21 09:15:47  27.925
  2015-08-21 10:15:47  28.495
  2015-08-21 11:15:47  27.596
  ...
  2016-08-10 07:19:24  16.944
  2016-08-10 08:19:24  27.149
  2016-08-10 09:19:24  28.152
  </code></pre>