Added

• More and better documentation
• OrderedDict.MustGet()
• Dict.MustGet()
• pytorch.LoadWithUnpickler() which allows loading PyTorch modules using a custom unpickler.
• Handle legacy method torch.nn.backends.thnn._get_thnn_function_backend when loading pytorch modules.

Changed

• FrozenSet implementation was modified, avoiding confusion with Set.
• Replace build CI job with tests and coverage
• Dict has been reimplemented using a slice, instead of a map, because in Go not all types can be map's keys (e.g. slices).
• Use Go version 1.15