MAINT: Make Bode plots more precise about the pole/zero discovery for discrete time systems

[ilayn]

This code

from harold import *
H = Transfer([0.05634, -0.00093524, -0.00093524, 0.05634],
             [ 1.       , -0.7631   , -0.1919863,  0.5434631], dt=1)

bode_plot(H)

gives

But in fact, say, bode_plot(H, np.logspace(-2, 0.2, 1000)) gives

Fix it please you self speaking person...