trivia

update copyright year

remove some unnecessary class hardcoding

fix functionally unimportant variable name in comprehension that is making pep8
complain

remove some unnecessary parentheses
add new ways to change Cookies' Cookie class

This was spurred by a suggestion by Laurent Bachelier (thanks, Laurent).

For those just tuning in, Cookies is an class which offers dict-like access to
collections of Cookie objects, each representing a name/value pair with its own
attributes (corresponding to attributes of an HTTP Cookie).

To make a cookie collection which constructs instances using your own class
(suppose it is called Scone) - use Cookies(_cookie_class=Scone).

To make a Cookies subclass generating instances which do the same thing,
override DEFAULT_COOKIE_CLASS on the subclass itself, and instantiate it
as normal.

It's also still possible to use the lower-level API to make whatever collection
interface you really want to use, if your requirements are really different.
add 3.4 and drop 3.1 (tox/pip breakage)

A backward-incompatible version bump comes with this.

None of the supporting test tools seem to actually support it any more
and those regressions show no signs of being fixed. 3.1 is a royal pain
anyway, not important in any distro I know of, and it was going to happen
someday, so why not now.
3.1 may still work, I'm just not interested in implied guarantees when
testing it is such a pain.

Sequenced this after _cookie_class so that can be in the new version