title: Resample daily pandas timeseries with start at time other than midnight
body: <p>I have a pandas timeseries of 10-min freqency data and need to find the maximum value in each 24-hour period. However, this 24-hour period needs to start each day at 5AM - not the default midnight which pandas assumes.</p>
  
  <p>I've been checking out <code>DateOffset</code> but so far am drawing blanks. I might have expected something akin to <code>pandas.tseries.offsets.Week(weekday=n)</code>, e.g. <code>pandas.tseries.offsets.Week(hour=5)</code>, but this is not supported as far as I can tell.</p>
  
  <p>I can do a nasty work around by <code>shift</code>ing the data first, but it's unintuitive and even coming back to the same code after just a week I have problems wrapping my head around the shift direction!</p>
  
  <p>Any more elegant ideas would be much appreciated.</p>