Use object.__hash__ for Node.__hash__

Use object.__hash__ for Node.__hash__

This fixes a regression in commit 60293416db69782fd048a7820667afa4ae7c423b that
changed the `__hash__` implementation of Node from the default pointer
hash, to a hash based on the node fields.

Since these fields contains list objects, they are not hashable, making
every call to `Node.__hash__` fail.

This breaks some third-party usage such as in `django-compressor`
(See: https://github.com/django-compressor/django-compressor/issues/1060)

This changed reverts the hash method back to using `object.__hash__` as
the hash implementation.