GroupBy.count() returns the grouping column as both index and column
`GroupBy.count()` (with the default `as_index=True`) return the grouping column both as index and as column, while other methods as `first` and `sum` keep it only as the index (which is most logical I think). This seems a minor inconsistency to me:

```
In [41]: data = pd.DataFrame({'name' : ['a', 'a', 'b', 'd'], 'counts' : [3,4,3,2]})
In [42]: data
Out[42]:
   counts name
0       3    a
1       4    a
2       3    b
3       2    d

In [43]: g = data.groupby('name')
In [45]: g.count()
Out[45]:
      counts  name
name
a          2     2
b          1     1
d          1     1

In [46]: g.first()
Out[46]:
      counts
name
a          3
b          3
d          2

In [47]: g.sum()
Out[47]:
      counts
name
a          7
b          3
d          2
```
