Use yarn and test with node 8

Author: danez

.travis.yml

@@ -1,9 +1,9 @@
 sudo: false
 language: node_js
 node_js:
-  - "4"
+  - "8"
   - "6"
-  - "7"
+  - "4"
 script:
-  - npm run lint
-  - npm test
+  - yarn lint
+  - yarn test

package.json

@@ -8,13 +8,13 @@
     "build:commonjs": "babel src/ --out-dir lib/ --ignore __tests__,__mocks__",
     "build:umd": "webpack --config webpack.build.js",
     "build:umd:min": "cross-env MINIFY=1 webpack --config webpack.build.js",
-    "build": "npm run clean && npm run build:commonjs",
-    "bundle": "mkdir -p dist && npm run build:umd && npm run build:umd:min",
+    "build": "yarn run clean && yarn run build:commonjs",
+    "bundle": "mkdir -p dist && yarn run build:umd && yarn run build:umd:min",
     "format": "prettier --write --single-quote --print-width 100 --trailing-comma all \"src/**/*.js\"",
     "lint": "eslint src",
     "precommit": "lint-staged",
-    "preversion": "npm run lint && npm test && npm run build && npm run bundle && git add dist/ && git diff --quiet --exit-code --cached || git commit -n -m 'publish: Distribution'",
-    "prepublish": "npm run build",
+    "preversion": "yarn run lint && yarn test && yarn run build && yarn run bundle && git add dist/ && git diff --quiet --exit-code --cached || git commit -n -m 'publish: Distribution'",
+    "prepublish": "yarn run build",
     "test": "jest",
     "start": "webpack-dev-server --inline --content-base examples/"
   },