Use node 8.4.x in production, 8.4.0 on Travis

.nvmrc

@@ -0,0 +1 @@
+8.4.0

.travis.yml

@@ -1,6 +1,4 @@
 language: node_js
-node_js:
-  - stable
 cache: yarn
 branches:
   only:

package.json

@@ -1,6 +1,5 @@
 {
   "private": true,
-  "name": "unpkg-website",
   "proxy": "http://localhost:3001",
   "scripts": {
     "start": "node scripts/start.js",
@@ -86,6 +85,9 @@
     "webpack-manifest-plugin": "1.1.0",
     "whatwg-fetch": "2.0.2"
   },
+  "engines": {
+    "node": "8.4.x"
+  },
   "jest": {
     "collectCoverageFrom": [
       "src/**/*.{js,jsx}"