test_get_sparameter_data(): also check contents
test_get_sparameter_data(): also check contents

The data from "simple_touchstone.s2p" now also checked for if the
correct S-parameter is returned.

jhillairet/scikit-rf,temmeand/scikit-rf,jhillairet/scikit-rf,jhillairet/scikit-rf,temmeand/scikit-rf,temmeand/scikit-rf,scikit-rf/scikit-rf,scikit-rf/scikit-rf