Upgraded to webpack v4

[gokulkrishh]

What's done:

• Added prettier, pre-commit stage.
• Moved from webpack v2 to v4.
• Updated few file names.
• Added netlify demo for each PR.
• Added DangerJS & Travis.

[gokulkrishh]

Deploy preview for qrcode-4951b7 ready!

Built with commit 1888e40

https://deploy-preview-57--qrcode-4951b7.netlify.com

[code-kotis-bot]

	Warnings
⚠️	asset size limit: The following asset(s) exceed the recommended size limit (244 KiB). This can impact web performance. Assets: decoder.js (3.38 MiB),webpack performance recommendations: You can limit the size of your bundles by using import() or require.ensure to lazy load some parts of your application. For more info visit https://webpack.js.org/guides/code-splitting/

	Messages
📖	🎉 The PR added 209908 and removed 49708 lines.
📖	Changed Files in this PR: .gitignore README.md app/css/styles.css app/index.html app/js/main.js app/js/snackbar.js app/js/vendor/qrscan.js package.json webpack.config.js yarn.lock

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