PEP 8 code format

Recently, I have some new CDN check logic to add, and will change some code in wafw00f/__init__.py, so maybe I want code format this file first.

Most of these commits are PEP 8 code format, like.

* trim trailing whitespace
* single or two blank lines
* using single quote if not docstring
* print () -> print()
* add some whitespace, make code more readable
* remove repeat "import random"
* remove wildcard import