DataFrame/Series.tz_convert with copy=False modifies original data
Hi. Not sure if it is a bug, or something which needs to be clarified. 

Consider the code

```
s = pd.Series(np.arange(0,5), index=pd.date_range('20131027', periods=5, freq='1H', tz='Europe/Berlin'))
s.tz_convert("UTC", copy=False)
```

`s` index is still the same as before.  If i do the same for frames.

```
d = pd.DataFrame(s)
d.tz_convert("UTC", copy=False)
```

This time index of `d` has changed. From the code it is not clear if `DataFrame` is doing the right thing either.

So is it a bug or is it just inconsistent, or is it an intention?

Update:

```
In [1]: s = pd.Series(np.arange(0,5), index=pd.date_range('20131027', periods=5, freq='1H', tz='Europe/Berlin'))
      s.tz_convert("UTC", copy=False)
Out[1]: 
2013-10-26 22:00:00+00:00    0
2013-10-26 23:00:00+00:00    1
2013-10-27 00:00:00+00:00    2
2013-10-27 01:00:00+00:00    3
2013-10-27 02:00:00+00:00    4
Freq: H, dtype: int32

In [2]: s
Out[2]: 
2013-10-27 00:00:00+02:00    0
2013-10-27 01:00:00+02:00    1
2013-10-27 02:00:00+02:00    2
2013-10-27 02:00:00+01:00    3
2013-10-27 03:00:00+01:00    4
Freq: H, dtype: int32

In [3]: d = pd.DataFrame(s)
      d.tz_convert("UTC", copy=False)
Out[3]: 
2013-10-26 22:00:00+00:00 0
2013-10-26 23:00:00+00:00 1
2013-10-27 00:00:00+00:00 2
2013-10-27 01:00:00+00:00 3
2013-10-27 02:00:00+00:00 4

In [214]: d
Out[214]: 
2013-10-26 22:00:00+00:00 0
2013-10-26 23:00:00+00:00 1
2013-10-27 00:00:00+00:00 2
2013-10-27 01:00:00+00:00 3
2013-10-27 02:00:00+00:00 4
```
