change hdf5 read function to use numpy
pandas has a security warning when using pytables and pickle to read binary streams: https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.read_hdf.html also creates another structure for pandas objects: https://stackoverflow.com/questions/33641246/pandas-cant-read-hdf5-file-created-with-h5py/33644128#33644128