BUG: Numpy Ufunc generates unintuitive AttributeError on object arrays
Example:

```
In [15]: np.log(Series([1,2,3,4], dtype='object'))
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-15-25deca6462b7> in <module>()
----> 1 np.log(Series([1,2,3,4], dtype='object'))

AttributeError: log
```

This is really a [numpy issue](http://projects.scipy.org/numpy/ticket/1013) (opened by Wes back in 2009, as Andy Hayden pointed out). But since object arrays are especially common in database output, as was the case in this [SO question](http://stackoverflow.com/questions/16968433/error-when-trying-to-apply-log-method-to-pandas-data-frame-column-in-python/1696849), there some places in pandas where we can help avoid this error.
