improve linting and add travis config

.eslintignore

+!.eslintrc.js
+src/vendor/*

.eslintrc.js

+module.exports = {
+  parser: "babel-eslint",
+  env: {
+    browser: true,
+    es6: true,
+    node: true
+  },
+  globals: {
+    THREE: true,
+    AFRAME: true,
+    NAF: true
+  },
+  plugins: ["prettier", "react"],
+  rules: {
+    "prettier/prettier": "error",
+    "prefer-const": "error",
+    "no-var": "error",
+    // Light console usage is useful but remove debug logs before merging to master.
+    "no-console": "off"
+  },
+  extends: ["prettier", "plugin:react/recommended", "eslint:recommended"]
+};

.eslintrc.json

-{
-  "parser": "babel-eslint",
-  "plugins": [
-    "prettier",
-    "react"
-  ],
-  "rules": {
-    "prettier/prettier": "error",
-    "prefer-const": "error",
-    "no-var": "error"
-  },
-  "extends": [
-    "prettier",
-    "plugin:react/recommended"
-  ]
-}

.travis.yml

+language: node_js
+install: yarn 
+script: yarn lint

package.json

@@ -11,7 +11,8 @@
     "postinstall": "node ./scripts/postinstall.js",
     "start": "cross-env NODE_ENV=development webpack-dev-server",
     "build": "rimraf ./public && cross-env NODE_ENV=production webpack --mode=production",
-    "prettier": "prettier --write src/**/*.js"
+    "prettier": "prettier --write src/**/*.js",
+    "lint": "eslint *.js src/**/*.js"
   },
   "dependencies": {
     "aframe-billboard-component": "^1.0.0",