Prevent leaked connections when broken 'EndRequestEvent' subscribers raise

Fixes #16 on the 2.13 branch.

Update setuptools and zc.buildout to currently-installable versions.

- setuptools 12.0.5
- zc.buildout 2.3.0

If base Python has  installed, mandate creating a virtualenv
without setuptools, and using it to bootstrap Zope.

See: http://blog.travis-ci.com/2014-12-17-faster-builds-with-container-based-infrastructure/

Trying to fix https://bugs.launchpad.net/zope2/+bug/1387225 changed format of self.args in superclass

Trying to fix bug https://bugs.launchpad.net/zope2/+bug/1387138. zope is trying to import a symbol which is not at the expected place anymore.

This implements the idea of the patch from
https://bugs.launchpad.net/zope2/+bug/143352
but also honours the trusted-proxy setting.

The unimportant events have changed names.