This commit bakes in a certain kind of representation for brush strokes:
c(t,s) = p(t) + R(theta(t)) b(t,s)
This representation allows us to cancel out some rotation terms when
computing the envelope equation, improving the efficiency of the
cusp-finding methods.
also includes the start of a way to observe which equations
are being solved, which should help with improving the performance of
the interval Newton method