message: Fix rustfmt command line.
diff: @@ -19,7 +19,7 @@ elif [ "$DOCS" = "yes" ]; then
  elif [ "$COVERAGE" = "yes" ]; then
  cargo tarpaulin --all --no-count --ciserver travis-ci --coveralls $TRAVIS_JOB_ID
  elif [ "$RUSTFMT" = "yes" ]; then
  - cargo fmt -- --write-mode diff
  + cargo fmt --all -- --check
  else
  cargo build $BUILD_ARGS --release
  cargo test $BUILD_ARGS --all --release
  