BUG: Timedelta repr does not show nanoseconds
Not sure this is intended, but `Timestamp` and `Timedelta` displays nanoseconds information inconsistently.
- `Timestamp` shows nanoseconds when it isn't 0

```
dt = pd.Timestamp(datetime.datetime.now())
h = pd.Timedelta(hours=1)

dt
#2015-01-21 00:01:05.260660
dt + offsets.Nano()
#2015-01-21 00:01:05.260660001
```
-  But `Timedelta` doesn't.

```
pd.Timedelta(nanoseconds=1)
#0 days 00:00:00.000000
pd.Timedelta(nanoseconds=1).nanoseconds
#1
```

I think `Timestamp` behavior is prefferable to avoid any misunderstanding. 
