wiggle_bisection
  Use bisection2 to estimate a solution to the wiggle equation.

  F(8) = -3.13768 (negative)
  F(0) = 3.1609 (positive)

  After 30 iterations:
  F(1.03868) = -4.31962e-07 (negative)
  F(1.03868) = 1.07018e-06 (positive)

  it <= itmax?  true
  |xn-xp| <= xtol?  true
  min(|f(xn)|,|f(xp)|) <= ftol?  true