Unused Imports in tseries.tools
Imports https://github.com/pydata/pandas/blob/master/pandas/tseries/tools.py#L213 and https://github.com/pydata/pandas/blob/master/pandas/tseries/tools.py#L214 are not used:

```
from pandas.tseries.offsets import DateOffset
from pandas.tseries.frequencies import (_get_rule_month, _month_numbers,
                                            _get_freq_str)
```

Is there any reason to leave these?
Is there an open ticket for removing unused imports?
