Run clippy in CI (nightly-only)

Author: tomhoule

.travis.yml

@@ -5,9 +5,10 @@ rust:
   - nightly
 cache: cargo
 before_script:
-  - if [ "$TRAVIS_RUST_VERSION" = "nightly" ]; then (rustup component add rustfmt-preview) fi
+  - if [ "$TRAVIS_RUST_VERSION" = "nightly" ]; then (rustup component add rustfmt-preview clippy-preview) fi
 script:
   - if [ "$TRAVIS_RUST_VERSION" = "nightly" ]; then (cargo fmt --all -- --check) fi
+  - if [ "$TRAVIS_RUST_VERSION" = "nightly" ]; then (cargo clippy) fi
   - cargo test --all
   - cargo build --manifest-path=./examples/github/Cargo.toml
   - cargo build --manifest-path=./graphql_client_cli/Cargo.toml