title: npm install removes react router from package-lock.json
body: <p>When I delete node_modules from my app, and then run npm install, my package-lock.json is changed and react-router is removed from it. I am getting errors that module react-router is not found. Before it was working perfectly. Here is my webpack-config:</p>
  
  <pre><code>`module.exports = {
    entry: ['whatwg-fetch', "./js/app.jsx"],
    output: { filename: "./js/out.js" },
    watch: true,
    devServer: {
    inline: true,
    contentBase: './',
    port: 3001
    },
    module: {
    loaders: [
        {
        test: /\.jsx$/, exclude: /node_modules/,
        loader: 'babel-loader',
        query: { presets: ['es2015', 'stage-2', 'react'] }
        },
        {
        test: /\.css$/,
        loader: 'style-loader!css-loader'
        }
      ]
    }
  }`
  </code></pre>
  
  <p>and my package.json </p>
  
  <pre><code>`{
    "name": "test",
    "version": "1.0.0",
    "description": "test",
    "main": "webpack.config.js",
    "scripts": {
      "test": "echo \"Error: no test specified\" &amp;&amp; exit 1",
      "start": "./node_modules/.bin/webpack-dev-server --hot"
    },
    "author": "test",
    "license": "ISC",
    "": {
      "babel-core": "^6.23.1",
      "babel-loader": "^6.3.2",
      "babel-preset-es2015": "^6.22.0",
      "babel-preset-react": "^6.23.0",
      "webpack": "^2.2.1"
    },
    "dependencies": {
      "react": "^15.4.0",
      "react-dom": "^15.4.0",
      "whatwg-fetch": "^2.0.3"
    },
    "devDependencies": {
      "babel-core": "^6.23.1",
      "babel-loader": "^6.3.2",
      "babel-preset-es2015": "^6.22.0",
      "babel-preset-react": "^6.23.0",
      "babel-preset-stage-2": "^6.24.1",
      "css-loader": "^0.28.11",
      "style-loader": "^0.21.0",
      "webpack": "^2.2.1",
      "webpack-dev-server": "^2.6.1"
    }
  }
  `
  </code></pre>