Truncate on series causes core dump when TZ is specified on index
Hello
I am getting a core dump when truncating a series with a timezone specified on the index.  Please see below:

This works fine:

```
import pandas
import datetime
import numpy as np    
rng = pandas.date_range('1/2/2005', '11/1/2010', freq='D')
ts = pandas.Series(np.random.randn(len(rng)), index=rng)
ts.truncate(datetime.datetime(2009,1,1), datetime.datetime(2011,1,1)).resample('D', how='sum')
```

However this core dumps for me:

```
import pandas
import datetime
import numpy as np    
rng = pandas.date_range('1/2/2005', '11/1/2010', freq='D', tz='US/Eastern')
ts = pandas.Series(np.random.randn(len(rng)), index=rng)
ts.truncate(datetime.datetime(2009,1,1), datetime.datetime(2011,1,1)).resample('D', how='sum')
```

The only difference is adding the TZ parameter to the date_range to set the index for a particular timezone. 

This was working fine in .15, but seems to be broken in .15.2

Thanks
