change travis engines

Author: fengwan

.travis.yml

@@ -10,15 +10,6 @@ jobs:
   allow_failures:
     - env: WEBPACK_VERSION=canary
   include:
-    - &test-latest
-      stage: Webpack latest
-      nodejs: 6
-      env: WEBPACK_VERSION=latest JOB_PART=test
-      script: npm run travis:$JOB_PART
-    - <<: *test-latest
-      nodejs: 4.8
-      env: WEBPACK_VERSION=latest JOB_PART=test
-      script: npm run travis:$JOB_PART
     - <<: *test-latest
       node_js: 8
       env: WEBPACK_VERSION=latest JOB_PART=lint