is DataFrame.apply using axis the wrong way around?
``` python
df = pd.DataFrame.from_dict({'a':'C C A'.split(),
                        'b':'C C A'.split(),
                        'c':'C A A'.split(),
                        'd':'C A A'.split()})
```

``` python
df.apply(len)
a    3
b    3
c    3
d    3
dtype: int64
```

``` python
df.apply(len, axis=1)
0    4
1    4
2    4
dtype: int64
```

The documentation says:

``` bash
Objects passed to functions are Series objects having index
either the DataFrame's index (axis=0) or the columns (axis=1).
Return type depends on whether passed function aggregates, or the
reduce argument if the DataFrame is empty.
```

That should mean that the above case with axis=0 should have [0,1,2] as index, doesn't it?

Version:
'0.13.1-492-g599156f'
