ENH: Named tuple fields as column names
Currently, passing a list of `namedtuple`s (or SQLAlchemy results, which is our specific case) to `DataFrame.from_records` doesn't resolve the field names. 

I think it would make sense to, at least if the names are all the same. Happy to do a PR if people agree.

``` python

In [17]: from collections import namedtuple

In [18]: Record = namedtuple('Record',('date','value'))

In [19]: records = [Record(d, v) for (d, v) in zip(pd.date_range('2000',freq='D', periods=20), range(20))]

In [20]: records
Out[20]: 
[Record(date=Timestamp('2000-01-01 00:00:00', offset='D'), value=0),
 Record(date=Timestamp('2000-01-02 00:00:00', offset='D'), value=1),
...
 Record(date=Timestamp('2000-01-19 00:00:00', offset='D'), value=18),
 Record(date=Timestamp('2000-01-20 00:00:00', offset='D'), value=19)]

In [21]: pd.DataFrame.from_records(records)
Out[21]: 
            0   1
0  2000-01-01   0
1  2000-01-02   1
...
18 2000-01-19  18
19 2000-01-20  19
```

Desired behavior:

``` python
Out[21]: 
            date   value
0  2000-01-01   0
1  2000-01-02   1
...
18 2000-01-19  18
19 2000-01-20  19
```
