refactor: remove npm install method

npm/README.md

-![Wiki.js](https://raw.githubusercontent.com/Requarks/wiki-site/1.0/assets/images/logo.png)
-
-# Wiki.js
-
-[![npm](https://img.shields.io/npm/v/wiki.js.svg?style=flat-square)](https://github.com/Requarks)
-[![Release](https://img.shields.io/github/release/Requarks/wiki.svg?style=flat-square&maxAge=3600)](https://github.com/Requarks/wiki/releases)
-[![License](https://img.shields.io/badge/license-AGPLv3-blue.svg?style=flat-square)](https://github.com/requarks/wiki/blob/master/LICENSE)
-
-This npm package is an installer for Wiki.js.  
-For information about Wiki.js, including detailed installation steps, read the following links:
-
-- [Official Website](https://wiki.js.org/)
-- [Installation Guide](https://wiki.js.org/get-started.html)
-- [GitHub Repository](https://github.com/Requarks/wiki)

npm/install.js

-'use strict'
-
-// =====================================================
-// Wiki.js
-// Installation Script
-// =====================================================
-
-const path = require('path')
-const spawn = require('child_process').spawn
-const installDir = path.resolve(__dirname, '../..')
-const cmd = (process.platform !== 'win32')
-  ? 'curl -s -S -o- https://wiki.js.org/install.sh | bash'
-  : `PowerShell.exe -NoProfile -ExecutionPolicy Bypass -Command "iex ((New-Object System.Net.WebClient).DownloadString('https://wiki.js.org/install.ps1'))"`
-
-console.info(`Executing installation script for ${process.platform} platform...`)
-
-let inst = spawn(cmd, [], {
-  cwd: installDir,
-  env: process.env,
-  shell: true,
-  stdio: 'inherit',
-  detached: true
-})
-
-inst.unref()

npm/package.json

-{
-  "name": "wiki.js",
-  "version": "1.0.5-rev.1",
-  "description": "A modern, lightweight and powerful wiki app built on NodeJS, Git and Markdown",
-  "main": "install.js",
-  "scripts": {
-    "test": "exit 1",
-    "postinstall": "node install.js"
-  },
-  "repository": {
-    "type": "git",
-    "url": "git+https://github.com/Requarks/wiki.git"
-  },
-  "keywords": [
-    "wiki",
-    "wikis",
-    "wikijs",
-    "wiki.js",
-    "wiki-js",
-    "docs",
-    "documentation",
-    "markdown",
-    "guides"
-  ],
-  "author": "Nicolas Giard",
-  "license": "AGPL-3.0",
-  "bugs": {
-    "url": "https://github.com/Requarks/wiki/issues"
-  },
-  "homepage": "https://github.com/Requarks/wiki#readme",
-  "dependencies": {}
-}