added Table.update_ids method

@wasade or @ElDeveloper, can one of you review this one? I haven't contributed to biom in a while - let me know if I'm doing anything wrong. The codebase is looking really nice, btw! 
what about:

```python
new_id = id_map.get(old_id, None)
if strict and new_id is None:
    raise TableException(...")
```