BUG: select_column does not preserve the column name
```
In [4]: df = DataFrame({'A' : np.random.randn(10), 'B' : 'foo'})

In [5]: df.to_hdf('test.h5','df',mode='w',format='table',data_columns=True)

# this should have a name of B
In [7]: with pd.HDFStore('test.h5') as store:
    print store.select_column('df','B')
   ...:     
0    foo
1    foo
2    foo
3    foo
4    foo
5    foo
6    foo
7    foo
8    foo
9    foo
dtype: object
```
