Use python-requests instead of urllib/urllib2/httplib

For much simpler/cleaner code.

I've signed the CLA, though I'm not exactly sure why it's necessary. This pull request contains vendored code authored by @kennethreitz and others, which is already Apache licensed, but they probably haven't signed the CLA (nor should they have to)

cf http://docs.python-requests.org/en/latest/

Note this is a fork of @intchanter's py3 work ( #18 ) so it depends upon that pull request being merged. This is because python-requests also requires python 2.6+, so this can't really be merged without his stuff.

(was https://github.com/intchanter/selenium/pull/1 )