refactor: simplify all yarn references in package.json and travis.yml

.travis.yml

@@ -4,7 +4,7 @@ notifications:
 language: node_js
 
 node_js:
-  - "8"
+  - "8.11.1"
 
 sudo: false
 
@@ -26,16 +26,16 @@ cache:
     - "node_modules"
 
 script:
-  - yarn run prettier -- --list-different
-  - yarn run lint
-  - yarn run jest --maxWorkers=4
+  - yarn prettier --list-different
+  - yarn lint
+  - yarn jest --maxWorkers=4
 
 after_success:
-  - yarn run codecov
+  - yarn codecov
 
 deploy:
   provider: script
-  script: curl -X POST -d '{}' $NETLIFY_DEPLOY_WEBHOOK && yarn run semantic-release
+  script: curl -X POST -d '{}' $NETLIFY_DEPLOY_WEBHOOK && yarn semantic-release
   skip_cleanup: true
   on:
     branch: master

package.json

@@ -10,13 +10,13 @@
     "clean-cache": "node bin/clean-cache.js",
     "heroku-push": "git push heroku master",
     "heroku-scheduler": "heroku addons:open scheduler",
-    "jest": "npm run clean-cache && cross-env NODE_ENV=test LOG_LEVEL=fatal jest",
+    "jest": "yarn clean-cache && cross-env NODE_ENV=test LOG_LEVEL=fatal jest",
     "lint-fix": "eslint --fix lib test",
     "lint": "eslint lib test",
     "prettier": "prettier \"**/*.{js,json,md}\" --write",
     "start": "node lib/renovate",
     "test-dirty": "git diff --exit-code",
-    "test": "npm run prettier -- --list-different && npm run lint && npm run jest"
+    "test": "yarn prettier --list-different && yarn lint && yarn jest"
   },
   "repository": {
     "type": "git",