Remove hard-coded length of position vector from robotstate.py
Remove hard-coded length of position vector from robotstate.py

mithrandir123/director,RussTedrake/director,mitdrc/director,openhumanoids/director,rdeits/director,mitdrc/director,empireryan/director,patmarion/director,gizatt/director,empireryan/director,rdeits/director,mithrandir123/director,gizatt/director,manuelli/director,edowson/director,manuelli/director,RobotLocomotion/director,patmarion/director,edowson/director,rdeits/director,patmarion/director,patmarion/director,gizatt/director,RobotLocomotion/director,rdeits/director,patmarion/director,mithrandir123/director,mithrandir123/director,mitdrc/director,mitdrc/director,mithrandir123/director,manuelli/director,edowson/director,RobotLocomotion/director,openhumanoids/director,RussTedrake/director,edowson/director,manuelli/director,mitdrc/director,edowson/director,empireryan/director,openhumanoids/director,RobotLocomotion/director,manuelli/director,openhumanoids/director,empireryan/director,gizatt/director,gizatt/director,RussTedrake/director,rdeits/director,RussTedrake/director,RussTedrake/director,empireryan/director,openhumanoids/director,RobotLocomotion/director