added 6D twist version that includes both linear and angular velocity

[wanglong06]

The current example considers controls on 4 DoF - (x, y, z, yaw). I am doing a project to control the total 6 DoF of a robot arm, which requires (x, y, z, roll, pitch, yaw). As a result, I extended the example by including the other two angular velocities.

[trainman419]

Cool! I think this will be a great help to a bunch of different users.

It seems like is a copy-paste of the existing node, with a few lines changed. Please extend the existing node instead of creating a completely new node. Keeping all of the code within a single node avoids two copies of the same code, and makes it easier to maintain in the future.

Please also update the README with instructions about how to use the new 6 DOF keys.

[wanglong06]

@trainman419 Hi Austin, I am glad you like the change I made. I was concerned by upgrading to 6 DoF, it may break others' applications that had refered to this repo, since so many people had forked.

But I agree with you that we should not maintain multiple copies of the same code. So please reject this pull and I am forking the repo again and will request another pull cleanly by only extending the single script file.