simplify travis.yml

Author: dongcai

.travis.yml

@@ -1,43 +1,24 @@
-dist: trusty
-
 language: node_js
 
 node_js:
   - "6"
-  - "stable"
-
-addons:
-  apt:
-    sources:
-    - ubuntu-toolchain-r-test
-    packages:
-    - gcc-4.8
-    - g++-4.8
-
-sudo: required
-
-before_install:
-  - sudo apt-get -qq update
-  - curl -o- -L https://yarnpkg.com/install.sh | bash
-  - export PATH="$HOME/.yarn/bin:$PATH"
+  - "8"
 
-install:
-  - yarn
+sudo: false
 
 before_script:
   - export DISPLAY=:99.0
   - sh -e /etc/init.d/xvfb start
   - export NODE_ENV=development
 
 cache:
-  yarn: true
   directories:
     - node_modules
 
 script:
-  - yarn lint
-  - yarn test
-  - yarn test-node
+  - npm run lint
+  - npm run test
+  - npm run test-node
 
 env:
   - TRAVIS=travis CXX=g++-4.8