updateSkel: computes the forward kinematics and jacobians for each
computeJ: computes the complete jacobian, J, that maps joint velocities to feature point velocities.
Roach specific calls:
buildRoach: top level script that puts the entire roach together
buildRoach calls:
buildBody: generates the first three links, namely the abdomen, the first thoracic segment, and the second and third segments (which are treated together as one link). This function calls newSkel() once to generate the abdoment, and then mountLink() 2 more times for the other two segments.
attachLeg: this is called 6 times to attach the six legs. Each time it is called, it calls mountLink() 4 times since there are 4 DOF per link.