Upgrade to Vuepress@next

Travis was failing with a weird ESLint error, and when I checked locally, the problem seemed to be related to Vuepress v0. Upgrading to Vuepress v1-alpha seems to fix this (at least on my machine...)

docs/.vuepress/config.js

@@ -14,7 +14,6 @@ module.exports = {
     ],
     dest: "dist",
     ga: "UA-100728112-1",
-    serviceWorker: true,
     themeConfig: {
 
         nav: [
@@ -129,11 +128,6 @@ module.exports = {
 
         // },
         lastUpdated: true,
-        serviceWorker: {
-
-            updatePopup: true,
-
-        },
         docsRepo: "pegjs/pegjs",
         docsDir: "docs",
         editLinks: true,

package.json

@@ -28,7 +28,7 @@
         "eslint": "5",
         "eslint-config-futagozaryuu": "5",
         "mocha": "5.2.0",
-        "vuepress": "0.14.8",
+        "vuepress": "next",
         "nyc": "13.1.0"
     },
     "engines": {