Drop support for Python 2.6

[jaraco]

Beginning with 705eea1, the tests started failing... because the updated version of portend dropped support for Python 2.6.

Additionally, packaging tools and other foundational packages will be dropping support for Python 2.6 soon too.

It's time for CherryPy to do the same.

[webknjaz]

There's a lot more legacy hacks yet to clean up. Shall we keep this issue open or create a new one for this?

[webknjaz]

Should we do the same to cheroot?

[jaraco]

I figure the legacy cleanup can happen at leisure. There are still pre-2.6 cruft in there that can go too. I don't think it needs to be ticketed.

We can do the same for cheroot soonish. No rush.

[webknjaz]

Alright, what about 3.2? It's also problematic. Are we going to drop it as well?

[webknjaz]

Oh.. And in setup.py we even claim support for 3.1, which I doubt anyone uses now as well.

[jaraco]

I'm not sure how Python 3.2 is problemmatic. If someone makes the case for dropping support, I imagine we could consider it. One area where there's still high demand for Python 3.2 support is in PyPy versions, though later versions have more modern interpreter support, so that's probably a non-issue.