Improvements for a release

It's enough for a new release for now but I have still a few things I want to improve (wheel support, using only release.py with a good documentation, help for writing the Changelog).

The major improvement are:

• auto-completion isn't a pain in the posterior anymore
• the tarball is something that can be uploaded to pypi, used by pip, etc. By using a temporary worktree, we are sure the sdist command won't collect files it should not.
• drop some unused stuff