Update to whitening defaults in TimeSeries.q_transform
Created by: alurban
@duncanmmacleod, this PR updates whitening defaults (and affected unit tests) under TimeSeries.q_transform
. This was missed in #891, but will properly restore the low-frequency content in the GW150914 spectrogram when run with default values, and should be released with GWPy 0.12.1.