title: "Module not found" when deploying React app to Heroku
body: <p>When I try to deploy my React app (made with create-react-app) to Heroku (using create-react-app-buildpack) I get the following error:</p>
  
  <pre><code>Failed to compile.
  Module not found: Error: Can't resolve 'jquery' in 
  '/tmp/build_049d73accaf035b451adf36ac44318d3/src/components'
  npm ERR! Linux 3.13.0-128-generic
  npm ERR! argv 
  "/tmp/build_049d73accaf035b451adf36ac44318d3/.heroku/node/bin/node" 
  "/tmp/build_049d73accaf035b451adf36ac44318d3/.heroku/node/bin/npm" "run" 
  "build"
  npm ERR! node v6.11.2
  npm ERR! npm  v3.10.10
  npm ERR! code ELIFECYCLE
  npm ERR! life-quality-data@0.1.0 build: `react-scripts build`
  npm ERR! Exit status 1
  </code></pre>
  
  <p>When testing on my computer everything works. I also have jQuery added as a dependency in <em>package.json</em>:</p>
  
  <pre><code>{
    "name": "life-quality-data",
    "version": "0.1.0",
    "private": true,
    "dependencies": {
      "axios": "^0.16.2",
      "dns": "^0.2.2",
      "fetch": "^1.1.0",
      "jquery": "^3.2.1",
      "node-sass-chokidar": "0.0.3",
      "numeral": "^2.0.6",
      "react": "^15.6.1",
      "react-dom": "^15.6.1",
      "react-router-dom": "^4.2.2",
      "react-scripts": "1.0.12",
      "xml2js": "^0.4.19"
    },
    "scripts": {
      "build-css": "node-sass-chokidar src/ -o src/",
      "watch-css": "npm run build-css &amp;&amp; node-sass-chokidar src/ -o src/ --watch --recursive",
      "start": "react-scripts start",
      "build": "react-scripts build",
      "test": "react-scripts test --env=jsdom",
      "eject": "react-scripts eject"
    }
  }
  </code></pre>
  
  <p>I think I might be missing a line. Also, could it be the <em>.gitignore</em>? Because on GitHub the node modules are being ignored.</p>