"AssertionError: Index length did not match values" when resampling with kind='period'
Should raise that `kind='period'` is not accepted for `DatetimeIndex` when resampling
Possible issue with period index resampling hanging (see @cpcloud example below)

version = 0.12.0.dev-f61d7e3

This bug also exists in 0.11.
## The bug

``` Python
In [20]: s.resample('T', kind='period')
-----------------
AssertionError  
Traceback (most recent call last)
<ipython-input-79-c290c0578332> in <module>()
----> 1 s.resample('T', kind='period')

/home/dk3810/workspace/python/pda/scripts/src/pandas/pandas/core/generic.py in resample(self, rule, how, axis, fill_method, closed, label, convention, kind, loffset, limit, base)
    255                               fill_method=fill_method, convention=convention,
    256                               limit=limit, base=base)
--> 257         return sampler.resample(self)
    258 
    259     def first(self, offset):

/home/dk3810/workspace/python/pda/scripts/src/pandas/pandas/tseries/resample.py in resample(self, obj)
     81 
     82         if isinstance(axis, DatetimeIndex):
---> 83             rs = self._resample_timestamps(obj)
     84         elif isinstance(axis, PeriodIndex):
     85             offset = to_offset(self.freq)

/home/dk3810/workspace/python/pda/scripts/src/pandas/pandas/tseries/resample.py in _resample_timestamps(self, obj)
    224             # Irregular data, have to use groupby
    225             grouped = obj.groupby(grouper, axis=self.axis)
--> 226             result = grouped.aggregate(self._agg_method)
    227 
    228             if self.fill_method is not None:

/home/dk3810/workspace/python/pda/scripts/src/pandas/pandas/core/groupby.py in aggregate(self, func_or_funcs, *args, **kwargs)
   1410         if isinstance(func_or_funcs, basestring):
-> 1411             return getattr(self, func_or_funcs)(*args, **kwargs)
   1412 
   1413         if hasattr(func_or_funcs, '__iter__'):

/home/dk3810/workspace/python/pda/scripts/src/pandas/pandas/core/groupby.py in mean(self)
    356         except Exception:  # pragma: no cover
    357             f = lambda x: x.mean(axis=self.axis)
--> 358             return self._python_agg_general(f)
    359 
    360     def median(self):

/home/dk3810/workspace/python/pda/scripts/src/pandas/pandas/core/groupby.py in _python_agg_general(self, func, *args, **kwargs)
    498                 output[name] = self._try_cast(values[mask],result)
    499 
--> 500         return self._wrap_aggregated_output(output)
    501 
    502     def _wrap_applied_output(self, *args, **kwargs):

/home/dk3810/workspace/python/pda/scripts/src/pandas/pandas/core/groupby.py in _wrap_aggregated_output(self, output, names)
   1473             return DataFrame(output, index=index, columns=names)
   1474         else:
-> 1475             return Series(output, index=index, name=self.name)
   1476 
   1477     def _wrap_applied_output(self, keys, values, not_indexed_same=False):

/home/dk3810/workspace/python/pda/scripts/src/pandas/pandas/core/series.py in __new__(cls, data, index, dtype, name, copy)
    494         else:
    495             subarr = subarr.view(Series)
--> 496         subarr.index = index
    497         subarr.name = name
    498 

/home/dk3810/workspace/python/pda/scripts/src/pandas/pandas/lib.so in pandas.lib.SeriesIndex.__set__ (pandas/lib.c:29775)()

AssertionError: Index length did not match values
```
## A workaround / expected behaviour

``` Python
In [81]: s.resample('T').to_period()
Out[81]: 
2013-04-12 19:15    325.000000
2013-04-12 19:16    326.899994
...
2013-04-12 22:58    305.600006
2013-04-12 22:59    320.444458
Freq: T, Length: 225, dtype: float32
```
## More information

``` Python

In [83]: s
Out[83]: 
2013-04-12 19:15:25    323
2013-04-12 19:15:28    NaN
...
2013-04-12 22:59:55    319
2013-04-12 22:59:56    NaN
2013-04-12 22:59:57    NaN
2013-04-12 22:59:58    NaN
2013-04-12 22:59:59    NaN
Name: aggregate, Length: 13034, dtype: float32

In [76]: s.index
Out[76]: 
<class 'pandas.tseries.index.DatetimeIndex'>
[2013-04-12 19:15:25, ..., 2013-04-12 22:59:59]
Length: 13034, Freq: None, Timezone: None

In [77]: s.head()
Out[77]: 
2013-04-12 19:15:25    323
2013-04-12 19:15:28    NaN
2013-04-12 19:15:29    NaN
2013-04-12 19:15:30    NaN
2013-04-12 19:15:31    327
Name: aggregate, dtype: float32

In [78]: s.resample('T')
Out[78]: 
2013-04-12 19:15:00    325.000000
2013-04-12 19:16:00    326.899994
...
2013-04-12 22:58:00    305.600006
2013-04-12 22:59:00    320.444458
Freq: T, Length: 225, dtype: float32

In [80]: pd.__version__
Out[80]: '0.12.0.dev-f61d7e3'

In [84]: type(s)
Out[84]: pandas.core.series.TimeSeries
```

(Please let me know if you need more info!  I'm using Ubuntu 13.04.  It's entirely possible that this isn't a bug but instead I am doing something stupid.  Oh, and let me take this opportunity to thank the Pandas dev team!  Pandas is awesome!!!  THANK YOU!)
