use latest drone config

.drone.yml

@@ -3,8 +3,14 @@ kind: pipeline
 type: docker
 name: test libpso
 
+concurrency:
+    limit: 1
+
+environment:
+  CARGO_INCREMENTAL: false
+
 steps:
-- name: cargo build
+- name: clean cache
   image: rustlang/rust:nightly
   volumes:
   - name: cache
@@ -12,8 +18,8 @@ steps:
   - name: target-cache
     path: /drone/src/target
   commands:
-  - cargo build 
-- name: cargo test
+  - cargo prune
+- name: build
   image: rustlang/rust:nightly
   volumes:
   - name: cache
@@ -21,7 +27,25 @@ steps:
   - name: target-cache
     path: /drone/src/target
   commands:
-  - cargo test
+  - cargo build
+- name: clippy!
+  image: rustlang/rust:nightly
+  volumes:
+  - name: cache
+    path: /usr/local/cargo
+  - name: target-cache
+    path: /drone/src/target
+  commands:
+  - cargo clippy -- --deny warnings
+- name: test
+  image: rustlang/rust:nightly
+  volumes:
+  - name: cache
+    path: /usr/local/cargo
+  - name: target-cache
+    path: /drone/src/target
+  commands:
+  - cargo test --jobs 1
 
 volumes:
 - name: cache
@@ -30,4 +54,3 @@ volumes:
 - name: target-cache
   host:
     path: /home/drone/cargo-cache
-