add into(DataFrame, pytables Table)

An addition to `into` so that one can go directly from a pytables Table to a pandas DataFrame.
it would be nice to create a pytest fixture here (though you don't have to)

```python
@pytest.yield_fixture
def h5():
    h5path = tempfile.mktemp(".h5")
    class Test(IsDescription):
        posted_dow = UInt8Col()
        jobtype  = UInt8Col()
        location  = UInt8Col()
        date  = StringCol(20)
        country  = StringCol(2)

    h5file = open_file(h5path, mode = "w", title = "Test file")
    group = h5file.create_group("/", 'test', 'Info')
    tab = h5file.create_table(group, 'sample', Test, "Example")
    arow = tab.row
    arow['country'] = 'ab'
    arow['date'] = '20121105'
    arow['location'] = 0
    arow['jobtype']  = 1
    arow['posted_dow']  = 3
    # Insert a new record
    arow.append()
    yield h5file
    # Close (and flush) the file
    h5file.close()
    if os.path.exists(h5path):
        os.remove(h5path)
```

then pass an `h5` parameter to your methods like so:

```python
def test_into_pytables_dataframe(self, h5):
    # awesome testing
```

it's a little weird at first because of the magic naming but it's more modular and less distracting than storing state in the test class