-rename Simulation.get_joint as get_sim_joint
-make JointSensor.__init__ be able to receive a Joint OR a SimulatedJoint, which
wraps a Joint. The idea is to avoid confusing calls such as "x.get_joint().get_joint()"
--move ./tests to ars/test and convert to a package? See
-dBodySetFiniteRotationAxis. is it necessary to set this if dBodySetFiniteRotationMode = true?
-rename package "model" to "core"?
+-split 'tests' and what are examples of how to use external libs
-move tests in utils.mathematical to a test file