#139 release 2.2.1 as a tarball

[Sébastien Barthélémy]

The svn has a tag corresponding to a 2.2.1 collada-dom release. However, this release does not appear on the downloads page.

Would it be possible to create packages for it? A simple source tarball would be enough to make the 2.2.1 release official and let the world know about it.