TEST: remove tests from _DocumentNTF.py
TEST: remove tests from _ds_freq.py
TEST: remove tests from deltasigma/_ds_optzeros.py
TEST: minor docstring change for consistency
TEST: remove tests from _ds_quantize.py
PEP8: fix indentation
TEST: remove tests from deltasigma/_ds_synNTFobj1.py
TEST: add test for f0=0, fix minor c&p error
TEST: remove tests from deltasigma/_dsclansNTF.py
TEST: move tests for delay() to the new location.