ix/loc using indices rather than labels when passed a list for integer MultiIndex DataFrame?
For an integer MultiIndex DataFrame, the ix and loc properties should use labels rather than indices, right? However, this seems not to be the case if ix/loc is passed a list containing multiple labels refering to a single level. That is, the following example

``` python
import numpy as np
import pandas as pd

index = pd.MultiIndex.from_product((np.arange(3), np.arange(3)), names=('level0', 'level1'))
columns = pd.Index(('column',))
data = pd.DataFrame(np.arange(9), index=index, columns=columns)
print('{}\n\n{}'.format(
    data.ix[0],
    data.ix[[0]]))
```

outputs

```
        column
level1        
0            0
1            1
2            2

               column
level0 level1        
0      0            0
```

whereas I would expect both `data.ix[0]` and `data.ix[[0]]` to output the first three rows. If I change the levels of the MultiIndex from integers to floats, the desired behaviour is obtained. That is, the modified example

``` python
import numpy as np
import pandas as pd

index = pd.MultiIndex.from_product((np.arange(3.), np.arange(3.)), names=('level0', 'level1'))
columns = pd.Index(('column',))
data = pd.DataFrame(np.arange(9), index=index, columns=columns)
print('{}\n\n{}'.format(
    data.ix[0.],
    data.ix[[0.]]))
```

outputs

```
        column
level1        
0            0
1            1
2            2

               column
level0 level1        
0      0            0
       1            1
       2            2
```

Did I miss some subtlety or is this indeed a bug?
