Python 3 compatibility

[telegraphic]

Convert to be Py3 compatible (not test very well but I can do S_sear_BL.py -h

For future ref, these two commands were very useful:

2to3 -w *.py
autopep8 PulsarSearch --recursive --select=E101,E121 --in-place

As there are indentation fixes, hard to tell what has actually changed