Since 0.13: passing pandas DataFrame/Series like numpy array breaks
As discussed in #6063: 
I noticed that that numpy-style access breaks sometimes under 0.13. While I haven't been able to pin-point the issue, calls like `pylab.hist(-df.ix[row, col_name])` fail with some `x[0]` index error and I have to use `pylab.hist(-df.ix[row, col_name]).values`.

Here is a csv file for which this happens: https://gist.github.com/8651509

``` python
plt.hist(pd.read_csv('debug.csv'))
```

produces:

``` python
--------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-203-b20a1ff5d1db> in <module>()
----> 1 hist(pd.load('debug.pickle'))

/home/ipython/envs/ipynb/local/lib/python2.7/site-packages/matplotlib/pyplot.pyc in hist(x, bins, range, normed, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, hold, **kwargs)
   2825                       histtype=histtype, align=align, orientation=orientation,
   2826                       rwidth=rwidth, log=log, color=color, label=label,
-> 2827                       stacked=stacked, **kwargs)
   2828         draw_if_interactive()
   2829     finally:

/home/ipython/envs/ipynb/local/lib/python2.7/site-packages/matplotlib/axes.pyc in hist(self, x, bins, range, normed, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, **kwargs)
   8247         # Massage 'x' for processing.
   8248         # NOTE: Be sure any changes here is also done below to 'weights'
-> 8249         if isinstance(x, np.ndarray) or not iterable(x[0]):
   8250             # TODO: support masked arrays;
   8251             x = np.asarray(x)

/home/ipython/envs/ipynb/local/lib/python2.7/site-packages/pandas/core/series.pyc in __getitem__(self, key)
    482     def __getitem__(self, key):
    483         try:
--> 484             result = self.index.get_value(self, key)
    485             if isinstance(result, np.ndarray):
    486                 return self._constructor(result,index=[key]*len(result)).__finalize__(self)

/home/ipython/envs/ipynb/local/lib/python2.7/site-packages/pandas/core/index.pyc in get_value(self, series, key)
   1030 
   1031         try:
-> 1032             return self._engine.get_value(s, k)
   1033         except KeyError as e1:
   1034             if len(self) > 0 and self.inferred_type == 'integer':

/home/ipython/envs/ipynb/local/lib/python2.7/site-packages/pandas/index.so in pandas.index.IndexEngine.get_value (pandas/index.c:2890)()

/home/ipython/envs/ipynb/local/lib/python2.7/site-packages/pandas/index.so in pandas.index.IndexEngine.get_value (pandas/index.c:2702)()

/home/ipython/envs/ipynb/local/lib/python2.7/site-packages/pandas/index.so in pandas.index.IndexEngine.get_loc (pandas/index.c:3440)()

/home/ipython/envs/ipynb/local/lib/python2.7/site-packages/pandas/hashtable.so in pandas.hashtable.Int64HashTable.get_item (pandas/hashtable.c:6595)()

/home/ipython/envs/ipynb/local/lib/python2.7/site-packages/pandas/hashtable.so in pandas.hashtable.Int64HashTable.get_item (pandas/hashtable.c:6536)()

KeyError: 0
```

While passing `.values` works.
