DataFrame with dtype=object converts Numpy Arrays to Series
Hi, i am not sure if this behaviour is a bug introduced in 0.13.1 or if it is supposed to be a new feature. If you store a numpy array into a DataFrame with `dtype=object` it is automatically converted into a Series instead of just staying the original array:

in:  `mytable = pd.DataFrame(data={'data':[np.array([1,2,3])]}, index=None, columns=None, dtype=object, copy=False)`
in: `type(mytable['data'][0])`
out: `<class 'pandas.core.series.Series'>`

In version 0.12.0 having the exact same statements, `mytable['data'][0]` would be of type `numpy.ndarray`. I would vote in favour of the old behaviour because stuff I put into an `object` frame should to remain the original object and not be autoconverted.

Thanks!
