title: missing column after pandas groupby
body: <p>I've got a pandas dataframe <code>df</code>. I group it by 3 columns, and count the results. When I do this I lose some information, specifically, the <code>name</code> column. This column is mapped 1:1 with the <code>desk_id</code> column. Is there anyway to include both in my final dataframe? </p>
  
  <p>here is the dataframe:</p>
  
  <pre><code>   shift_id    shift_start_time      shift_end_time        name                   end_time       desk_id  shift_hour
  0  37423064 2014-01-17 08:00:00 2014-01-17 12:00:00  Adam Scott 2014-01-17 10:16:41.040000  15557987           2
  1  37423064 2014-01-17 08:00:00 2014-01-17 12:00:00  Adam Scott 2014-01-17 10:16:41.096000  15557987           2
  2  37423064 2014-01-17 08:00:00 2014-01-17 12:00:00  Adam Scott 2014-01-17 10:52:17.402000  15557987           2
  3  37423064 2014-01-17 08:00:00 2014-01-17 12:00:00  Adam Scott 2014-01-17 11:06:59.083000  15557987           3
  4  37423064 2014-01-17 08:00:00 2014-01-17 12:00:00  Adam Scott 2014-01-17 08:27:57.998000  15557987           0
  </code></pre>
  
  <p>I group it like this:</p>
  
  <pre><code>grouped = df.groupby(['desk_id', 'shift_id', 'shift_hour']).size()
  grouped = grouped.reset_index()
  </code></pre>
  
  <p>And here is the result, missing the <code>name</code> column.</p>
  
  <pre><code>    desk_id  shift_id  shift_hour  0
  0  14468690  37729081           0  7
  1  14468690  37729081           1  3
  2  14468690  37729081           2  6
  3  14468690  37729081           3  5
  4  14468690  37729082           0  5
  </code></pre>
  
  <p>Also, anyway to rename the count column as 'count' instead of '0'?</p>