- add a link to DH resources

- demonstrate that robot uses only a single landmark for localization;
  look at robot.is_localized_to

For grad:
  modify world_viewer to show a joint?  or show lift?

  add a "world" joint to represent cozmo in the world, for IK

  write kine.solve for the lift

  add "show kine shoulder" to show full parameters for a specific joint