Add clippy to Travis CI

Author: damienmg

.ci/build.sh

@@ -11,4 +11,7 @@ case "$1" in
   doc)
     cargo doc --all
     ;;
-esac
+  clippy)
+    cargo clippy --all-targets --all-features -- -D warnings
+    ;;
+esac

.ci/setup.sh

@@ -1,9 +1,16 @@
 #!/bin/bash
 
-if [ "$1" == "format" ]; then
-  echo "Installing rustfmt..."
-  rustup toolchain install nightly
-  rustup component add --toolchain nightly rustfmt-preview
-  which rustfmt || cargo install --force rustfmt-nightly
-  cargo +nightly fmt -- --version
-fi
+case "$1" in
+  format)
+    echo "Installing rustfmt..."
+    rustup toolchain install nightly
+    rustup component add --toolchain nightly rustfmt-preview
+    which rustfmt || cargo install --force rustfmt-nightly
+    cargo +nightly fmt -- --version
+    ;;
+  clippy)
+    echo "Installing clippy..."
+    rustup toolchain install nightly
+    rustup component add clippy --toolchain=nightly || cargo install --git https://github.com/rust-lang/rust-clippy/ --force clippy
+    ;;
+esac