Memory Performance Regression in 0.13+
The following snippit runs fine in pandas 0.12 on a machine with 8GB of RAM but throws a `MemoryError` on a machine with 16GB of RAM when using pandas 0.13

``` python
date_index = pd.date_range('01-Jan-2012', '23-Jan-2013', freq='T')
daily_dates = date_index.to_period('D').to_timestamp('S','S')
fracofday = date_index.view(np.ndarray) - daily_dates.view(np.ndarray)
fracofday = fracofday.astype('timedelta64[ns]').astype(np.float64)/864e11
fracofday = pd.TimeSeries(fracofday, daily_dates)
index = pd.date_range(date_index.min().to_period('A').to_timestamp('D','S'),
                      date_index.max().to_period('A').to_timestamp('D','E'),
                      freq='D')
temp = pd.TimeSeries(1.0, index)
fracofday *= temp[fracofday.index]
```
