Don't build documentation for the binary, just the lib
Don't build documentation for the binary, just the lib

This enables one to locally do

    $ cargo doc

and get library level documentation. Without the changes, cargo doesn't know
whether to build docs for the binary or library, and so instead it gives an
error and stops.

emilio/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen,emilio/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen