Py3 for pywin scanner, multiple paths for base scanner, doc on watch_paths and a bit PEP8

As the title and the comments say, this is what I have done:

- First I fixed some formatting according to PEP8, not too fussy. I also added some missing docstring where it has been easy :)
- Then I fixed two minor problems in the pywin_scanner.py for Python 3.
  - Replaced `_thread` with `threading`
  - and using `queue` for 3 (renamed from `Queue`)
- Fixed a bug that occured when using the base scanner with multiple paths
- And mentioned the ability of watch more then one path in the `README.rst` the only and one documentation on sniffer.

Hoping everybody is fine with it and there are not too many bugs ;)