Use npm on travis-ci.

We are having some caching issues with yarn and chromedriver.

.travis.yml

@@ -11,15 +11,14 @@ node_js:
   - "4"
   - "6"
 cache:
-  yarn: true
   directories:
     - node_modules
-install:
-  - curl -o- -L https://yarnpkg.com/install.sh | bash
-  - export PATH=$HOME/.yarn/bin:$PATH
-  - yarn --ignore-engines
+before_install:
+  - rm yarn.lock
 before_script:
   - export DISPLAY=:99.0
   - sh -e /etc/init.d/xvfb start
   - sleep 3
+script:
+  - echo "No need to use npm test since it's done in the install section via 'npm prepublish'"
 after_script: npm run coveralls

package.json

@@ -23,14 +23,15 @@
   },
   "scripts": {
     "build": "gulp",
+    "release": "gulp release",
     "pretestonly": "chromedriver &",
     "testonly": "NODE_PATH=test/lib jest test/unit/*.test.js test/isolated/*.test.js test/integration/**/test/*.test.js",
     "posttestonly": "pkill chromedriver",
-    "pretest": "npm run lint && NODE_ENV=test npm run prepublish",
+    "pretest": "npm run lint && NODE_ENV=test npm run release",
     "test": "npm run testonly -- --coverage --forceExit",
     "coveralls": "nyc --instrument=false --source-map=false report --temp-directory=./coverage --reporter=text-lcov | coveralls",
     "lint": "standard 'bin/*' 'client/**/*.js' 'examples/**/*.js' 'lib/**/*.js' 'pages/**/*.js' 'server/**/*.js' 'test/**/*.js'",
-    "prepublish": "npm run lint && gulp release && npm run testonly -- --forceExit",
+    "prepublish": "npm run test && npm run release",
     "precommit": "npm run lint"
   },
   "standard": {