Update README and CONTRIBUTING docs (#7)

Update README and CONTRIBUTING docs (#7)

* Update links to point to the SPDX github pages

Signed-off-by: Gary O'Neall <gary@sourceauditor.com>
* Fix broken link in README per https://github.com/wking/fsf-api/pull/23

Signed-off-by: Gary O'Neall <gary@sourceauditor.com>
* Update CONTRIBUTING.md file

Signed-off-by: Gary O'Neall <gary@sourceauditor.com>
* Update copyright date

Signed-off-by: Gary O'Neall <gary@sourceauditor.com>
* Apply suggestions from code review

General clean up of the README file

Co-authored-by: CAM Gerlach <CAM.Gerlach@Gerlach.CAM>
* Remove the gh-pages pull request information - this will soon be done in the CI

Signed-off-by: Gary O'Neall <gary@sourceauditor.com>
* Add (Expat) to the MIT license title per suggestion

Co-authored-by: CAM Gerlach <CAM.Gerlach@Gerlach.CAM>
* Cleanup CONTRIBUTING.md per suggestions

Co-authored-by: CAM Gerlach <CAM.Gerlach@Gerlach.CAM>
Co-authored-by: CAM Gerlach <CAM.Gerlach@Gerlach.CAM>