Bump to Next@5, remove unneeded config

next.config.js

@@ -1,13 +0,0 @@
-const Uglify = require('uglifyjs-webpack-plugin')
-
-module.exports = {
-  // TODO remove `next.configs.js` when this closes: https://github.com/zeit/next.js/issues/1195
-  webpack: function(c, { dev }) {
-    if (!dev) {
-      c.plugins = c.plugins.filter(plugin => plugin.constructor.name !== 'UglifyJsPlugin')
-      c.plugins.push(new Uglify())
-    }
-
-    return c
-  }
-}

package.json

@@ -22,6 +22,7 @@
     "codemirror": "^5.31.0",
     "codemirror-graphql": "^0.6.12",
     "codemirror-mode-elixir": "^1.1.1",
+    "cross-env": "^5.1.3",
     "dom-to-image": "^2.5.2",
     "downshift": "^1.28.0",
     "dropperx": "^0.1.0",
@@ -33,7 +34,7 @@
     "morgan": "^1.8.2",
     "morphmorph": "^0.0.2",
     "ms": "^2.0.0",
-    "next": "^4.2.3",
+    "next": "^5.0.0",
     "react": "^16.2.0",
     "react-click-outside": "^3.0.0",
     "react-codemirror2": "^3.0.7",
@@ -51,14 +52,12 @@
   },
   "devDependencies": {
     "all-contributors-cli": "^4.7.0",
-    "cross-env": "^5.1.1",
     "cypress": "^1.4.1",
     "hex2rgb": "^2.2.0",
     "husky": "^0.14.3",
     "lint-staged": "^6.0.0",
     "now": "^9.2.7",
     "prettier": "^1.8.1",
-    "uglifyjs-webpack-plugin": "1.1.2",
     "webpack": "^3.10.0"
   },
   "now": {