Improve hoomd.box.Box.__{n}eq__ methods
Improve hoomd.box.Box.__{n}eq__ methods

Use Python buildin constant ``NotImplemented`` if the compared object is
not of a ``Box`` instance.

joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue,joaander/hoomd-blue