Unable to retrieve same-index dataframe with the last item per group
The original thread is [here](http://stackoverflow.com/questions/25046252/filling-in-with-the-last-entry-of-the-group?noredirect=1#comment38958154_25046252). 

``` python
> df
                   C         D  E
A    B                           
bar  one   -1.350006  0.260339  2
     three -0.236451 -0.056614  0
flux six   -0.515571 -0.155078  1
     three -0.365032  1.055669  2
foo  five   1.145811  1.514191  0
     one   -0.108427 -0.643262  2
     two    0.286897  0.405798  2
     two   -1.452286  1.149264  2
```

The goal is to get a dataframe with the same index with each entry having the last value in the groups associated with `A`, i.e.

```
> df
                   C         D  E
A    B                           
bar  one   -0.236451 -0.056614  2
     three -0.236451 -0.056614  2
flux six   -0.365032  1.055669  2
     three -0.365032  1.055669  2
foo  five  -1.452286  1.149264  2
     one   -1.452286  1.149264  2
     two   -1.452286  1.149264  2
     two   -1.452286  1.149264  2
```

However, none of the following work:
- `df.groupby(level='A').apply(lambda x: x[-1])`
- `df.groupby(level='A').transform(pd.Series.last)`
- `df.groupby(level='A').transform(lambda x: x.iloc[-1])`
