BUG: Fix renaming of columns in into(DataFrame, Series)

How this currently works:

```python
In [1]: df = pd.DataFrame(columns=['a'])

In [2]: s = pd.Series([1, 2, 3])

In [3]: df
Out[3]:
Empty DataFrame
Columns: [a]
Index: []

In [4]: s
Out[4]:
0    1
1    2
2    3
dtype: int64

In [5]: from blaze import into

In [6]: into(df, s)
Out[6]:
   0
0  1
1  2
2  3
```

How it should work, given that `interactive.py` uses this code to display the result of a `Field` expression

```python
In [6]: into(df, s)
Out[6]:
   a
0  1
1  2
2  3
```