Pure python apply broken with TimeGrouper
```

In [12]: s.convert('D', how='count')
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
/home/wesm/code/pandas/<ipython-input-12-52597b6f97c4> in <module>()
----> 1 s.convert('D', how='count')

/home/wesm/code/pandas/pandas/core/generic.pyc in convert(self, rule, method, how, axis, as_index, closed, label)
    179                 how = translate_grouping(how)
    180 
--> 181             result = grouped.agg(how)
    182         else:
    183             # upsampling

/home/wesm/code/pandas/pandas/core/groupby.pyc in agg(self, func, *args, **kwargs)
    246         See docstring for aggregate
    247         """
--> 248         return self.aggregate(func, *args, **kwargs)
    249 
    250     def _iterate_slices(self):

/home/wesm/code/pandas/pandas/core/groupby.pyc in aggregate(self, func_or_funcs, *args, **kwargs)
   1263         """
   1264         if isinstance(func_or_funcs, basestring):
-> 1265             return getattr(self, func_or_funcs)(*args, **kwargs)
   1266 
   1267         if hasattr(func_or_funcs,'__iter__'):

/home/wesm/code/pandas/pandas/core/groupby.pyc in wrapper(*args, **kwargs)
    178                 return self.apply(curried_with_axis)
    179             except Exception:
--> 180                 return self.apply(curried)
    181 
    182         return wrapper

/home/wesm/code/pandas/pandas/core/groupby.pyc in apply(self, func, *args, **kwargs)
    237         applied : type depending on grouped object and function
    238         """
--> 239         return self._python_apply_general(func, *args, **kwargs)
    240 
    241     def aggregate(self, func, *args, **kwargs):

/home/wesm/code/pandas/pandas/core/groupby.pyc in _python_apply_general(self, func, *args, **kwargs)
    409 
    410         return self._wrap_applied_output(result_keys, result_values,
--> 411                                          not_indexed_same=not_indexed_same)
    412 
    413     def _wrap_applied_output(self, *args, **kwargs):

/home/wesm/code/pandas/pandas/core/groupby.pyc in _wrap_applied_output(self, keys, values, not_indexed_same)
   1335                                         not_indexed_same=not_indexed_same)
   1336         else:
-> 1337             return Series(values, index=_get_index())
   1338 
   1339     def _aggregate_named(self, func, *args, **kwargs):

/home/wesm/code/pandas/pandas/core/groupby.pyc in _get_index()
   1319                 index = MultiIndex.from_tuples(keys, names=key_names)
   1320             else:
-> 1321                 ping = self.grouper.groupings[0]
   1322                 if len(keys) == ping.ngroups:
   1323                     index = ping.group_index

AttributeError: 'TimeGrouper' object has no attribute 'groupings'

In [13]: s.convert('D', how='count')
```
