changed a try/except statement for debugging, shouldn't have commited
put back the try/except statement
fixed a bug in no_distortion, one of the variable names was mistyped
on initializing pt, now if a z_object is input then set_z_object is called, which sets z, zerr and freq
fixed mistyped variable in remove_distortion.  Also, the outputs of remove_distortion are now the distortion tensor and a new z_object with distortion removed.