bin/get-github-release.go: enable extraction of binary not in root of tar
bin/get-github-release.go: enable extraction of binary not in root of tar

Also fix project name regexp to allow -

ncw/rclone,B4dM4n/rclone,B4dM4n/rclone,B4dM4n/rclone,olihey/rclone,olihey/rclone,ncw/rclone,ncw/rclone,olihey/rclone,olihey/rclone,ncw/rclone,B4dM4n/rclone