PyTables open_file method.

Examples
--------
>>> bar = pd.DataFrame(np.random.randn(10, 4))
>>> store = pd.HDFStore('test.h5')
>>> store['foo'] = bar   # write to HDF5
>>> bar = store['foo']   # retrieve
>>> store.close()

**Create or load HDF5 file in-memory**

When passing the `driver` option to the PyTables open_file method through
**kwargs, the HDF5 file is loaded or created in-memory and will only be
written when closed:

>>> bar = pd.DataFrame(np.random.randn(10, 4))
>>> store = pd.HDFStore('test.h5', driver='H5FD_CORE')
>>> store['foo'] = bar
>>> store.close()   # only now, data is written to disk
z