API: behaviour of label indexing with floats on integer index
from #12246 

@jorisvandenbossche this looks odd

```
In [11]: s = pd.Series([1,2,3])

In [12]: s.loc[0.0] = 10

In [13]: s.loc[0.0]
TypeError: cannot do label indexing on <class 'pandas.indexes.range.RangeIndex'>
 with these indexers [0.0] of <type 'float'>
```
