Setuptools < 36.8.0 no longer supported by PyPI

Due to the [deprecation of non-SNI support on PyPI](https://github.com/pypa/pypi-support/issues/978) buildout bootstrapping is currently broken.

The fix requires obtaining a patched setuptools for this as zc.buildout can't work with newer versions; we can backport [the original change](https://github.com/pypa/setuptools/pull/1190/files) and have bootstrap work from the patched version.

Until someone gets round to this, however, this project is not going to be usable by anyone not already bootstrapped.

Start by reading the linked PyPI support issue and the original setuptools pull request 1190, then trace the buildout bootstrapping process described in the issue. Done means a fresh bootstrap works on PyPI with a patched setuptools version while remaining compatible with zc.buildout.

索引モデルが issue の本文から書いたものです。