DataFrame.hist() doesn't work for DataFrame with only 1 column
## This is in version 0.7.1

In [209]: a = DataFrame(np.asarray([1,2,3,4,5]).T)

In [210]: a
Out[210]:
   0
0  1
1  2
2  3
3  4
4  5

In [211]: a.hist()
TypeError                                 Traceback (most recent call last)
H:<ipython-input-211-351515a79fe3> in <module>()
----> 1 a.hist()

C:\Python27\lib\site-packages\pandas\core\frame.pyc in hist(self, grid, *_kwds)
   3923
   3924         for i, col in enumerate(_try_sort(self.columns)):
-> 3925             ax = axes[i / k][i % k]
   3926             ax.hist(self[col].dropna().values, *_kwds)
   3927             ax.set_title(col)

TypeError: 'AxesSubplot' object does not support indexing
