Pin down zc.buildout and setuptools versions in order to fix test setups

Pin down zc.buildout and setuptools versions in order to fix bogus "bad constraint" errors caused by `setuptools==8.0`.

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**Background**:

The recently released `zc.buildout==2.3` now requires `setuptools==8.0`. This `setuptools` version [includes changes](https://pypi.python.org/pypi/setuptools#id4) to the version parsing logic according to [PEP 440](http://legacy.python.org/dev/peps/pep-0440/).

Some of these changes cause (at least) one combination of a constraint (version pin) and requirement (from `setup.py`) from the Plone KGS to fail. This combination is the
- constraint for `five.localsitemanager` to `2.0.5` from the [Plone KGS](http://dist.plone.org/release/4.3-latest/versions.cfg) and the
- requirement `five.localsitemanager > 2.0dev` from [`five.grok`'s `setup.py`](https://github.com/zopefoundation/five.grok/blob/master/setup.py#L44).

With the new setuptools version, the immediate version comparison `parse_version('2.0.5') > parse_version('2.0dev')` still yields `True`, but comparing whether version `2.0.5` is in the specification `>2.0dev` fails:
- `'2.0.5' in Specification('>2.0dev')` -> `False`.

/cc @jone @maethu @phgross @deiferni