update drone

.drone.yml

@@ -1,21 +1,8 @@
 pipeline:
-  restore-cache:
+  build:
-    image: drillster/drone-volume-cache
+    image: node:latest
-    restore: true
-    mount:
-      - ./node_modules
-    volumes:
-      - /tmp/cache:/cache
-
-  install:
-    image: node:8.6.0
     commands:
-      - node -v
+      - node --version
-      - npm -v
+      - npm --version
       - npm install
-
-  testing:
-    image: node:8.6.0
-    group: testing
-    commands:
       - npm run test