docs(CONTRIBUTING.md): fix url to clippy upstream repo to point to https://github.com/rust-lang-nursery/rust-clippy instead of https://github.com/Manishearth/rust-clippy
docs(CONTRIBUTING.md): fix url to clippy upstream repo to point to https://github.com/rust-lang-nursery/rust-clippy instead of https://github.com/Manishearth/rust-clippy

kbknapp/clap-rs,kbknapp/clap-rs