Public spec repo

Peter Williams <peter.williams@...>

We have completed our transition the linux foundation's
infrastructure. This final piece was having a publicly cloneable git
repository for the spec. This is now in place.

This should make it easier for everyone to contribute to the
improvement of spdx. To that end, i published a contributions howto
on the wiki: <>. Please
try it out and see if it works for you. If you see ways to improve
the howto feel free to edit that page.