Sdistmaker

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- Documentation update.

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- Setup.py cleanup.

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- Replacing base and base_on_server the right way around, now.

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- Cleaning up the tempdir after we're finished with it. And cd'ing out of
that dir before zapping it.

- Using buildout's bin/python so that we get setuptools also when run on the
server where there's no global setuptools. This assumes we're always run
within buildout: fine with me.

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- Added sdist_from_tags script for creating all tarballs.

- Added make_sdist script for creating a single sdist.

- Initial library skeleton created by thaskel.