Upgrade for new requests version

[prabcs]

Ref: john-kurkowski#145
Merging ^ here in my master to be able to use it until ^ gets merged and versioned.

This PR intends to provide the ability to the session to find the cacert.pem file required by requests. It makes find_first_response work in the case when tldextract, requests, certifi are all bundled in one .egg/.zip file and the code is run from that bundle leading to this error -

File "./packages-e79cd9628c5bca67379a4f131d342e8420480100.egg/tldextract/tldextract.py", line 329, in extract
    return TLD_EXTRACTOR(url)
  File "./packages-e79cd9628c5bca67379a4f131d342e8420480100.egg/tldextract/tldextract.py", line 209, in __call__
    suffix_index = self._get_tld_extractor().suffix_index(translations)
  File "./packages-e79cd9628c5bca67379a4f131d342e8420480100.egg/tldextract/tldextract.py", line 249, in _get_tld_extractor
    raw_suffix_list_data = find_first_response(self.suffix_list_urls)
  File "./packages-e79cd9628c5bca67379a4f131d342e8420480100.egg/tldextract/remote.py", line 38, in find_first_response
    text = session.get(url).text
  File "./packages-e79cd9628c5bca67379a4f131d342e8420480100.egg/requests/sessions.py", line 521, in get
    return self.request('GET', url, **kwargs)
  File "./packages-e79cd9628c5bca67379a4f131d342e8420480100.egg/requests/sessions.py", line 508, in request
    resp = self.send(prep, **send_kwargs)
  File "./packages-e79cd9628c5bca67379a4f131d342e8420480100.egg/requests/sessions.py", line 618, in send
    r = adapter.send(request, **kwargs)
  File "./packages-e79cd9628c5bca67379a4f131d342e8420480100.egg/requests/adapters.py", line 407, in send
    self.cert_verify(conn, request.url, verify, cert)
  File "./packages-e79cd9628c5bca67379a4f131d342e8420480100.egg/requests/adapters.py", line 226, in cert_verify
    "invalid path: {0}".format(cert_loc))
IOError: Could not find a suitable TLS CA certificate bundle, invalid path: ./packages-e79cd9628c5bca67379a4f131d342e8420480100.egg/certifi/cacert.pem