Final round of PyTables

Why not the following?

```Python
>>> dtype_to_pytables(dt)  # doctest: +SKIP
{'amount': Int32Col(shape=(), dflt=0, pos=1),
 'name': StringCol(itemsize=7, shape=(), dflt='', pos=0),
 'time': Time64Col(shape=(), dflt=0.0, pos=2)}
```