.loc indexing with list of list or array fail
I wonder to know if the following is an excepted behaviour:

``` python
arrays = [[3, 3, 5, 5, 7, 8, 9, 9, 9],
          [1, 2, 2, 8, 8, 1, 2, 4, 5]]
tuples = list(zip(*arrays))

df = pd.DataFrame(np.random.randn(9, 4), index=arrays)
print(df)
```

```
            0         1         2         3
3 1 -0.406271 -0.365945  1.014546  0.193454
  2 -1.433601 -2.398783  0.421473  1.183917
5 2  0.358215  0.183478  1.327390  1.846286
  8 -0.054229  1.476181 -2.193220 -0.945004
7 8 -0.598960  0.191141  1.245808 -0.614519
8 1  1.051352 -0.537377 -0.534096  0.319221
9 2  0.784284  1.561996  0.258979  1.344247
  4 -0.348615  0.410410  0.152473 -1.153719
  5  1.524407 -0.184949 -0.732762  0.186657
```

Now I want to retrieve some data with multi indexing.

``` python
# It works
indexes = [tuple([3, 1]), tuple([5, 8])]
df.loc[indexes]
```

``` python
# It fails
indexes = np.array([[3, 1], [5, 8]])
df.loc[indexes]
```

```
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-12-d91db2bf1d2a> in <module>()
      1 indexes = np.array([[3, 1], [5, 8]])
----> 2 df.loc[indexes]

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/core/indexing.py in __getitem__(self, key)
   1127             return self._getitem_tuple(key)
   1128         else:
-> 1129             return self._getitem_axis(key, axis=0)
   1130 
   1131     def _getitem_axis(self, key, axis=0, validate_iterable=False):

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/core/indexing.py in _getitem_axis(self, key, axis, validate_iterable)
   1248 
   1249             if hasattr(key, 'ndim') and key.ndim > 1:
-> 1250                 raise ValueError('Cannot index with multidimensional key')
   1251 
   1252             if validate_iterable:

ValueError: Cannot index with multidimensional key
```

``` python
# It fails
indexes = [[3, 1], [5, 8]]
df.loc[indexes]
```

```

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-10-be34675485dc> in <module>()
      1 indexes = [[3, 1], [5, 8]]
----> 2 df.loc[indexes]

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/core/indexing.py in __getitem__(self, key)
   1127             return self._getitem_tuple(key)
   1128         else:
-> 1129             return self._getitem_axis(key, axis=0)
   1130 
   1131     def _getitem_axis(self, key, axis=0, validate_iterable=False):

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/core/indexing.py in _getitem_axis(self, key, axis, validate_iterable)
   1252             if validate_iterable:
   1253                 self._has_valid_type(key, axis)
-> 1254             return self._getitem_iterable(key, axis=axis)
   1255         elif _is_nested_tuple(key, labels):
   1256             locs = labels.get_locs(key)

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/core/indexing.py in _getitem_iterable(self, key, axis)
    901                 level = None
    902 
--> 903             keyarr_is_unique = Index(keyarr).is_unique
    904 
    905             # existing labels are unique and indexer is unique

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/lib.cpython-34m.so in pandas.lib.cache_readonly.__get__ (pandas/lib.c:36059)()

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/core/index.py in is_unique(self)
    453     @cache_readonly(allow_setting=True)
    454     def is_unique(self):
--> 455         return self._engine.is_unique
    456 
    457     def is_integer(self):

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/index.cpython-34m.so in pandas.index.IndexEngine.is_unique.__get__ (pandas/index.c:4026)()

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/index.cpython-34m.so in pandas.index.IndexEngine._do_unique_check (pandas/index.c:4442)()

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/index.cpython-34m.so in pandas.index.IndexEngine._ensure_mapping_populated (pandas/index.c:4615)()

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/index.cpython-34m.so in pandas.index.IndexEngine.initialize (pandas/index.c:4703)()

/home/hadim/.virtualenvs/st/lib/python3.4/site-packages/pandas/hashtable.cpython-34m.so in pandas.hashtable.PyObjectHashTable.map_locations (pandas/hashtable.c:11720)()

TypeError: unhashable type: 'list'
```
