DateRange in docs not working
```
rng = DateRange(start, end, offset=BDay())

```

triggers:
NameError: name 'BDay' is not defined

should be

```
rng = DateRange(start, end, offset=datetools.BDay())
```

http://pandas.pydata.org/pandas-docs/stable/timeseries.html#generating-date-ranges-daterange
