[ODE] Joint tutorial for ODE?

[Russ Smith]

> I was wondering if you could update the documentation on joints anytime
> soon - for instance, a tutorial on how the ball and socket joint
> constraint is derived.

i think i'll make this my next task, as i don't feel like coding right now
(after two weeks not coding, i feel like i've forgotten how!). i have a
partial draft already, it might take a week or so to put it all together.
it'll assume the reader knows the basics of vector and matrix algebra.

russ.

--
Russ Smith
http://www.q12.org