Make package.json work with Cloud Foundry

This does three things:

1. Pins newer Node and NPM versions
2. Runs `npm run build` instead of the Heroku build script.
3. Moves devDependencies into dependencies. These are required for
   the build script, so it makes no sense for them to be in the
   devDependencies section, because production apps NEED TO BE BUILT.
   These sections were being treated as build-time and run-time
   dependencies. I am not sure if this was a misuse of NPM or whether
   NPM inherently conflates the relationship of dev and prod with that
   of build-time and run-time dependencies. You decide.

package.json

@@ -10,7 +10,7 @@
     "standard": "node ./node_modules/standard/bin/cmd.js",
     "dev": "webpack --config webpack.config.js --progress --colors --watch",
     "build": "webpack --config webpack.production.js --progress --colors --bail",
-    "postinstall": "bin/heroku",
+    "postinstall": "npm run build",
     "start": "node app.js",
     "doctoc": "doctoc --title='# Table of Contents' README.md"
   },
@@ -19,8 +19,15 @@
     "archiver": "^2.1.1",
     "async": "^2.1.4",
     "aws-sdk": "^2.7.20",
-    "base64url": "^3.0.0",
     "azure-storage": "^2.7.0",
+    "babel-cli": "^6.18.0",
+    "babel-core": "^6.21.0",
+    "babel-loader": "^6.2.10",
+    "babel-plugin-transform-runtime": "^6.15.0",
+    "babel-polyfill": "^6.22.0",
+    "babel-preset-es2015": "^6.18.0",
+    "babel-runtime": "^6.20.0",
+    "base64url": "^3.0.0",
     "blueimp-md5": "^2.6.0",
     "body-parser": "^1.15.2",
     "bootstrap": "^3.3.7",
@@ -34,12 +41,20 @@
     "connect-session-sequelize": "^4.1.0",
     "cookie": "0.3.1",
     "cookie-parser": "1.4.3",
+    "copy-webpack-plugin": "^4.0.1",
+    "css-loader": "^0.26.1",
     "deep-freeze": "^0.0.1",
     "diff-match-patch": "git+https://github.com/hackmdio/diff-match-patch.git",
+    "doctoc": "^1.3.0",
     "ejs": "^2.5.5",
+    "ejs-loader": "^0.3.0",
     "emojify.js": "~1.1.0",
+    "exports-loader": "^0.6.3",
+    "expose-loader": "^0.7.1",
     "express": ">=4.14",
     "express-session": "^1.14.2",
+    "extract-text-webpack-plugin": "^1.0.1",
+    "file-loader": "^0.9.0",
     "file-saver": "^1.3.3",
     "flowchart.js": "^1.6.4",
     "font-awesome": "^4.7.0",
@@ -49,8 +64,10 @@
     "handlebars": "^4.0.6",
     "helmet": "^3.3.0",
     "highlight.js": "~9.12.0",
+    "html-webpack-plugin": "^2.25.0",
     "i18n": "^0.8.3",
     "imgur": "git+https://github.com/hackmdio/node-imgur.git",
+    "imports-loader": "^0.7.0",
     "ionicons": "~2.0.1",
     "jquery": "^3.1.1",
     "jquery-mousewheel": "^3.1.13",
@@ -60,7 +77,11 @@
     "js-url": "^2.3.0",
     "js-yaml": "^3.7.0",
     "jsdom-nogyp": "^0.8.3",
+    "json-loader": "^0.5.4",
+    "jsonlint": "^1.6.2",
     "keymaster": "^1.6.2",
+    "less": "^2.7.1",
+    "less-loader": "^2.2.3",
     "list.js": "^1.5.0",
     "lodash": "^4.17.4",
     "lz-string": "1.4.4",
@@ -79,8 +100,8 @@
     "markdown-it-sup": "^1.0.0",
     "markdown-pdf": "^8.0.0",
     "mathjax": "~2.7.0",
-    "mermaid": "~7.1.0",
     "mattermost": "^3.4.0",
+    "mermaid": "~7.1.0",
     "meta-marked": "^0.4.2",
     "method-override": "^2.3.7",
     "minimist": "^1.2.0",
@@ -90,6 +111,7 @@
     "mysql": "^2.12.0",
     "node-uuid": "^1.4.7",
     "octicons": "~4.4.0",
+    "optimize-css-assets-webpack-plugin": "^1.3.0",
     "passport": "^0.4.0",
     "passport-dropbox-oauth2": "^1.1.0",
     "passport-facebook": "^2.1.1",
@@ -99,8 +121,8 @@
     "passport-ldapauth": "^2.0.0",
     "passport-local": "^1.0.0",
     "passport-oauth2": "^1.4.0",
-    "passport-twitter": "^1.0.4",
     "passport-saml": "^0.31.0",
+    "passport-twitter": "^1.0.4",
     "passport.socketio": "^3.7.0",
     "pdfobject": "^2.0.201604172",
     "pg": "^6.1.2",
@@ -111,6 +133,7 @@
     "readline-sync": "^1.4.7",
     "request": "^2.79.0",
     "reveal.js": "~3.6.0",
+    "script-loader": "^0.7.0",
     "scrypt": "^6.0.3",
     "select2": "^3.5.2-browserify",
     "sequelize": "^3.28.0",
@@ -120,22 +143,29 @@
     "socket.io-client": "~2.0.4",
     "spin.js": "^2.3.2",
     "sqlite3": "^4.0.1",
+    "standard": "^9.0.1",
     "store": "^2.0.12",
     "string": "^3.3.3",
+    "string-loader": "^0.0.1",
+    "style-loader": "^0.13.1",
     "tedious": "^1.14.0",
     "to-markdown": "^3.0.3",
     "toobusy-js": "^0.5.1",
+    "url-loader": "^0.5.7",
     "uuid": "^3.1.0",
     "uws": "~0.14.1",
     "validator": "^10.4.0",
     "velocity-animate": "^1.4.0",
     "visibilityjs": "^1.2.4",
     "viz.js": "^1.7.0",
+    "webpack": "^1.14.0",
+    "webpack-parallel-uglify-plugin": "^0.2.0",
     "winston": "^2.3.0",
     "xss": "^1.0.3"
   },
   "engines": {
-    "node": ">=6.x <10.x"
+    "node": "8.x.x",
+    "npm": ">=5.x.x"
   },
   "bugs": "https://github.com/hackmdio/codimd/issues",
   "keywords": [