Install wheels via setuptools, fixes #425

Remove no longer existing winbot

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Fixed: could not install eggs with case issues

Setuptools 38.2.0 suddenly started supporting and downloading wheels.
.whl files would end up in the non-functioning and deprecated unpack_wheel().
The new default ('just use setuptools') works fine.

- If you use an older setuptools, setuptools won't download wheels and the new
  code won't be used.

- If you use buildout.wheel, you'll overwrite the unpacker anyway.

For instance when sdist file name and package name had different case.

Update implicit-parts.rst

miss {

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Use HTTPS for default PyPI index

PyPI redirects HTTP to HTTPS by default now so using HTTPS directly
avoids the potential for that redirect being modified in flight,
helping prevent MITM attacks.

Fixes #114.

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Egg `zope.testing` is already a dependency of `zc.buildout[test]`.

Add missing egg `coverage` to part that imports coverage on
initialization.

Fix #153: buildout should cache working set environments

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Fixes #397.

tox will produce the coverage reports by default.

This fixes #392.

Previously under Python 3 (probably prior to 3.6, when dicts became
ordered by default) or under Python 2 with ``-R`` or
``PYTHONHASHSEED=random`` the results were undefined because dict
iteration order is undefined.

The value being sorted is complex and defined by
pkg_resources.Distribution:

```    @property
    def hashcmp(self):
        return (
            self.parsed_version,
            self.precedence,
            self.key,
            _remove_md5_fragment(self.location),
            self.py_version or '',
            self.platform or '',
        )

    def __hash__(self):
        return hash(self.hashcmp)

    def __lt__(self, other):
        return self.hashcmp < other.hashcmp
...
```