fix: throw error when install from npm

Author: peakchen90

.travis.yml

@@ -10,6 +10,7 @@ node_js:
 install:
   - npm install
   - npm install -g codecov
+  - npm run test:install
 
 stages:
   - test

package.json

@@ -13,10 +13,10 @@
   "scripts": {
     "test": "jest",
     "test:clear-cache": "jest --clearCache",
+    "test:install": "node test/install.js && node playground/install.js",
     "pg:dev": "node playground/build.js --dev",
     "pg:build": "node playground/build.js",
-    "prepublishOnly": "npm run test",
-    "postinstall": "node test/install.js && node playground/install.js"
+    "prepublishOnly": "npm run test"
   },
   "husky": {
     "hooks": {