Pandas pytables interface doesn't create empty table datasets
Pandas used to allow the writing of empty HDF5 datasets through its pytables interface code. However, after upgrading to 0.17 (from 0.11), we've discovered that this behaviour is intentionally
short circuited. The library behaves as though the dataset is being written, but simply ignores the request and the resulting HDF5 file doesn't contain the requested table.

The offending code is in pandas/io/pytables.py:_write_to_group()

```
    # we don't want to store a table node at all if are object is 0-len
    # as there are not dtypes
    if getattr(value, 'empty', None) and (format == 'table' or append):
        return
```

We've worked around it by patching our installed copy of pandas, but we'd like to know the provocation behind this code before submitting a pull request. The comment implies that the lack of dtypes in the dataset is the cause, however each pandas column has type information even if empty.

Any clarification would be appreciated
