Fix the default value for the error tolerance
Fix the default value for the error tolerance

The default value for the error tolerance should be `1.0e-4`
(= 1.0 × 10⁻⁴), not `10.0e-4` (= 10.0 × 10⁻⁴ = 1.0 × 10⁻³). Thus, the
example root approximation in the documentation comments is now correct.

kristorres/Sakura