Updating python-requests and python-urllib3

[Christopher Baines <chris@cbaines.net>]

I have had a go at updating python-requests to the latest upstream
release (from 2.8.1 to 2.9.1). This bundles the latest version of
python-urllib3 (1.13.1) so I have updated that also (from 1.12 to 1.13.1).

1: https://tracker.debian.org/pkg/requests
2: https://tracker.debian.org/pkg/python-urllib3

When updating python-urllib3, I also added in the DEP8 tests from
#796717 [3]. I duplicated the test, and adjusted it for python 3 (as the
patch was just python 2 only).

3: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=796717

I am still getting to grips with git-dpm (previously I have just used
git buildpackage). So I may have made some mistakes when attempting to
update to the latest versions. Its also probably prudent to have the
python-requests package depend on the latest version of python-urllib3
(which I have not changed). You can find the updated repositories here
[4], [5].

4: http://git.cbaines.net/python-requests/
5: http://git.cbaines.net/python-urllib3/

Thanks,

Chris