H5 is broken

[evanberkowitz]

> ./action-comparison.py --h5 test.h5 produces a TypeError: cannot pickle 'dict_keys' object error.

The only dictionary keys object introduced recently is point_group_irreps. Running with --log-level DEBUG indeed produces a few errors

2023-10-09 15:09:42,409 supervillain.h5                     DEBUG Writing /0.500000/Villain/Action/Lattice/point_group_weights/('E', 1) as numpy.
2023-10-09 15:09:42,409 supervillain.h5                     ERROR 'tuple' object has no attribute 'encode'
2023-10-09 15:09:42,409 supervillain.h5                     DEBUG Writing /0.500000/Villain/Action/Lattice/point_group_weights/('E', 1) by pickling.
2023-10-09 15:09:42,409 supervillain.h5                     ERROR 'tuple' object has no attribute 'encode'
2023-10-09 15:09:42,410 supervillain.h5                     DEBUG Writing /0.500000/Villain/Action/Lattice/point_group_weights by pickling.
2023-10-09 15:09:42,410 supervillain.h5                     ERROR Unable to create link (name already exists)
2023-10-09 15:09:42,444 supervillain.h5                     DEBUG Writing /0.500000/Villain/Action/Lattice by pickling.
2023-10-09 15:09:42,445 supervillain.h5                     ERROR cannot pickle 'dict_keys' object

So this should be fixed before any script (#63) can be written!