BUG: Panel.iloc[] bug with MultiIndex axis (another one)
I'd expect the [7] to produce the same result as [6], but instead it gives an error.

```
Python 3.4.0 (v3.4.0:04f714765c13, Mar 16 2014, 19:25:23) [MSC v.1600 64 bit (AMD64)]
Type "copyright", "credits" or "license" for more information.

IPython 2.1.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: from numpy import zeros

In [2]: from pandas import Panel, MultiIndex

In [3]: p1 = Panel(zeros((3,3,3)), items=['a','b','c'], major_axis=['x','y','z'], minor_axis=['u','v','w'])

In [4]: mi = MultiIndex.from_tuples([(0,'x'), (1,'y'), (1,'z')])

In [5]: p2 = Panel(zeros((3,3,3)), items=['a','b','c'], major_axis=mi, minor_axis=['u','v','w'])

In [6]: p1.iloc[:, 1, 0]
Out[6]:
a    0
b    0
c    0
Name: u, dtype: float64

In [7]: p2.iloc[:, 1, 0]
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-7-f7c04712ad2b> in <module>()
----> 1 p2.iloc[:, 1, 0]

C:\Python34\lib\site-packages\pandas\core\indexing.py in __getitem__(self, key)
   1125     def __getitem__(self, key):
   1126         if type(key) is tuple:
-> 1127             return self._getitem_tuple(key)
   1128         else:
   1129             return self._getitem_axis(key, axis=0)

C:\Python34\lib\site-packages\pandas\core\indexing.py in _getitem_tuple(self, tup)
   1332                 continue
   1333
-> 1334             retval = getattr(retval, self.name)._getitem_axis(key, axis=axis)
   1335
   1336             # if the dim was reduced, then pass a lower-dim the next time

C:\Python34\lib\site-packages\pandas\core\indexing.py in _getitem_axis(self, key, axis, validate_iterable)
   1386                 self._is_valid_integer(key, axis)
   1387
-> 1388             return self._get_loc(key, axis=axis)
   1389
   1390     def _convert_to_indexer(self, obj, axis=0, is_setter=False):

C:\Python34\lib\site-packages\pandas\core\indexing.py in _get_loc(self, key, axis)
     87
     88     def _get_loc(self, key, axis=0):
---> 89         return self.obj._ixs(key, axis=axis)
     90
     91     def _slice(self, obj, axis=0, typ=None):

C:\Python34\lib\site-packages\pandas\core\panel.py in _ixs(self, i, axis)
    803         if _is_list_like(key):
    804             indexer = {self._get_axis_name(axis): key}
--> 805             return self.reindex(**indexer)
    806
    807         # a reduction

C:\Python34\lib\site-packages\pandas\core\panel.py in reindex(self, items, major_axis, minor_axis, **kwargs)
   1109                       else kwargs.pop('minor', None))
   1110         return super(Panel, self).reindex(items=items, major_axis=major_axis,
-> 1111                                           minor_axis=minor_axis, **kwargs)
   1112
   1113     @Appender(_shared_docs['rename'] % _shared_doc_kwargs)

C:\Python34\lib\site-packages\pandas\core\generic.py in reindex(self, *args, **kwargs)
   1622         # perform the reindex on the axes
   1623         return self._reindex_axes(axes, level, limit,
-> 1624                                   method, fill_value, copy).__finalize__(self)
   1625
   1626     def _reindex_axes(self, axes, level, limit, method, fill_value, copy):

C:\Python34\lib\site-packages\pandas\core\generic.py in _reindex_axes(self, axes, level, limit, method, fill_value, copy)
   1639             ax = self._get_axis(a)
   1640             new_index, indexer = ax.reindex(
-> 1641                 labels, level=level, limit=limit, method=method)
   1642
   1643             obj = obj._reindex_with_indexers(

C:\Python34\lib\site-packages\pandas\core\index.py in reindex(self, target, method, level, limit, copy_if_needed)
   3256             else:
   3257                 # hopefully?
-> 3258                 target = MultiIndex.from_tuples(target)
   3259
   3260         return target, indexer

C:\Python34\lib\site-packages\pandas\core\index.py in from_tuples(cls, tuples, sortorder, names)
   2809                 tuples = tuples.values
   2810
-> 2811             arrays = list(lib.tuples_to_object_array(tuples).T)
   2812         elif isinstance(tuples, list):
   2813             arrays = list(lib.to_object_array_tuples(tuples).T)

C:\Python34\lib\site-packages\pandas\lib.pyd in pandas.lib.tuples_to_object_array (pandas\lib.c:52859)()

TypeError: object of type 'numpy.int64' has no len()
```
