TimeSeries.take loses tz
```
In [24]: ts2.index
Out[24]: 
<class 'pandas.tseries.index.DatetimeIndex'>
freq: <1 Day>, timezone: US/Central
[1990-01-01 00:00:00-06:00, ..., 2000-01-01 00:00:00-06:00]
length: 3653

In [25]: ts2.take(range(5)).index
Out[25]: 
DatetimeIndex([1990-01-01 00:00:00, 1990-01-02 00:00:00, 1990-01-03 00:00:00,
       1990-01-04 00:00:00, 1990-01-05 00:00:00], dtype=datetime64[us])
```
