title: python pandas timedelta specific rows
body: <p>I have a dataframe of a season's worth of basketball scores and I would like to find the number of days between games for each team for every game they have played in the season.</p>
  
  <p>Example frame:</p>
  
  <pre><code>  testDateFrame = pd.DataFrame({'HomeTeam': ['HOU', 'CHI', 'DAL', 'HOU'],
                            'AwayTeam' : ['CHI', 'DAL', 'CHI', 'DAL'],
                            'HomeGameNum': [1, 2, 2, 2],
                            'AwayGameNum' : [1, 1, 3, 3],
                            'Date' : [datetime.date(2014,3,11), datetime.date(2014,3,12),     datetime.date(2014,3,14), datetime.date(2014,3,15)]})
  </code></pre>
  
  <p>My desired output is this:</p>
  
  <pre><code>  AwayGameNum AwayTeam Date  HomeGameNum HomeTeam AwayRest  HomeRest
          1      CHI  2014-03-11    1      HOU        nan       nan
          1      DAL  2014-03-12    2      CHI        nan        0
          3      CHI  2014-03-14    2      DAL         1         1
          3      DAL  2014-03-15    2      HOU         0         3 
  </code></pre>
  
  <p>Where the AwayRest, HomeRest columns are the number of days between games for the AwayTeam, HomeTeam -1</p>