* Add test for HandReach-v0 serialization
* Fix HandReach-v0 serialization
* Add test_{manipulate,manipulate_touch_sensors}.py
* Fix v2 -> v3 mujoco test naming
* Skip hand tests if `skip_mujoco`
* Fix v2 to v3 conversion test naming
* Use pytest.mark.skipif instead of unittest.skipIf
* SKIP_MUJOCO_MESSAGE -> SKIP_MUJOCO_WARNING_MESSAGE rename
* fix skipif argument name for hand serialization tests