tempted to make the ``.ix`` cases the same (e.g. fix (11)).

again ``s.ix[2:5]`` is the reason we have ``iloc/loc``.

```
In [9]: s.ix[2:5]
Out[9]: 
5.0     2
7.5     3
10.0    4
dtype: int64

In [10]:  s.ix[2.0:5.0]
Out[10]: 
2.5    1
5.0    2
dtype: int64

In [11]: s.ix[2.0:5]
Out[11]: 
5.0     2
7.5     3
10.0    4
dtype: int64

In [12]: s.ix[2.1:5]
Out[12]: 
2.5    1
5.0    2
dtype: int64
```