Replace urllib2 components in got3, pep8

[eilifm]

Substative Changes:
Replace urllib2 components with equivalent urllib3 components.
For example:

        if proxy:
            opener = urllib.request.build_opener(urllib.request.ProxyHandler(
                {'http': proxy, 'https': proxy}), urllib.request.HTTPCookieProcessor(cookieJar))
        else:
            opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cookieJar))
        opener.addheaders = headers

Style Changes:
Ran PEP8 autostyle tool to convert tabs to spaces and other standard styling changes.