user: Extend github_authorize() documentation
user: Extend github_authorize() documentation

Susurrus/crates.io,achanda/crates.io,rust-lang/crates.io,rust-lang/crates.io,steveklabnik/crates.io,achanda/crates.io,steveklabnik/crates.io,achanda/crates.io,steveklabnik/crates.io,rust-lang/crates.io,steveklabnik/crates.io,Susurrus/crates.io,Susurrus/crates.io,rust-lang/crates.io,achanda/crates.io,Susurrus/crates.io