Column mismatch in DataFrame of Series silently produces empty DataFrame
The following behavior surprised me.  Of course there might be a good reason for it.  Thought I'd report, feel free to close if it's not appropriate.

``` Python
In [1]: from pandas import DataFrame, Series

In [2]: s = Series([1, 2, 3], name='foo')

In [3]: DataFrame(s, columns=['bar'])
Out[3]: 
Empty DataFrame
Columns: [bar]
Index: []
```
