Python libraries required only for specific command-line options are now only loaded when those options are specified.

Signed-off-by: Sharif Olorin <sio@tesser.org>
Older versions of numpy didn't have a percentile function, and it was in scipy instead.
This change attempts to fall back to scipy if the function is missing.

Signed-off-by: Sharif Olorin <sio@tesser.org>