The input impulse used to drive the impulse response of a discrete-time system should be unit area rather than unit height. With this change, the discrete-time system's impulse response matches the cont-time systems's, if the discrete time system was sampled with 'impulse-equivalent' approximation according to:

sysd = sys.sample(0.1, 'impulse')

A new unit test checks this.

(this is consistent with MATLAB behavior)

Update: rewrote summary, last version was written after a long work session and it shows : )