add clippy to ci

.drone.yml

@@ -7,7 +7,7 @@ concurrency:
     limit: 1
 
 steps:
-- name: cargo build
+- name: build
   image: rustlang/rust:nightly
   volumes:
   - name: cache
@@ -16,7 +16,16 @@ steps:
     path: /drone/src/target
   commands:
   - cargo build
-- name: cargo test
+- name: clippy!
+  image: rustlang/rust:nightly
+  volumes:
+  - name: cache
+    path: /usr/local/cargo
+  - name: target-cache
+    path: /drone/src/target
+  commands:
+  - cargo clippy
+- name: test
   image: rustlang/rust:nightly
   volumes:
   - name: cache