Update contributing guidelines with correct repository URLs

Author: preston176

CONTRIBUTING.md

@@ -1,7 +1,7 @@
 ## Contributing
 
-[fork]: https://github.com/github/REPO/fork
-[pr]: https://github.com/github/REPO/compare
+[fork]: https://github.com/github/GreenSoftwareDirectory/fork
+[pr]: https://github.com/github/GreenSoftwareDirectory/compare
 [style]: https://github.com/styleguide/ruby
 
 Hi there! We're thrilled that you'd like to contribute to this project. Your help is essential for keeping it great.