Update lint-staged to the latest version 🚀 (#50)

## The devDependency [lint-staged](https://github.com/okonet/lint-staged) was updated from `7.3.0` to `8.0.0`.
This version is **not covered** by your **current version range**.

If you don’t accept this pull request, your project will work just like it did before. However, you might be missing out on a bunch of new features, fixes and/or performance improvements from the dependency update.

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<details>
<summary>Release Notes for v8.0.0</summary>

<h1><a href="http://git+https/github.com/okonet/lint-staged/compare/v7.3.0...v8.0.0" rel="nofollow">8.0.0</a> (2018-10-29)</h1>
<h3>Features</h3>
<ul>
<li>Add support for partially staged files (<a href="http://git+https/github.com/lint-staged/lint-staged/issues/75" rel="nofollow">#75</a>) (<a href="http://git+https/github.com/okonet/lint-staged/commit/f82443c" rel="nofollow">f82443c</a>), closes <a href="http://git+https/github.com/lint-staged/lint-staged/issues/62" rel="nofollow">#62</a></li>
</ul>
<h3>BREAKING CHANGES</h3>
<ul>
<li>Node &gt;= 8.6 is required</li>
</ul>
</details>

<details>
<summary>Commits</summary>
<p>The new version differs by 5 commits.</p>
<ul>
<li><a href="https://urls.greenkeeper.io/okonet/lint-staged/commit/f82443c7f7b147aae11e65a797b280ce375c8515"><code>f82443c</code></a> <code>feat: Add support for partially staged files (#75)</code></li>
<li><a href="https://urls.greenkeeper.io/okonet/lint-staged/commit/e6a6ec66af26a4fa505279fac937f076687777e7"><code>e6a6ec6</code></a> <code>chore: upgrade to jest 23 (#507)</code></li>
<li><a href="https://urls.greenkeeper.io/okonet/lint-staged/commit/f05ada6c8f5190999df1ac036fcc647dc9ca624e"><code>f05ada6</code></a> <code>docs: Add an example for type checking with flow (#502)</code></li>
<li><a href="https://urls.greenkeeper.io/okonet/lint-staged/commit/bcd0af4467a6da98ab4f115f5a0b987030e7c93c"><code>bcd0af4</code></a> <code>docs: Add SurviveJS link</code></li>
<li><a href="https://urls.greenkeeper.io/okonet/lint-staged/commit/d782fa199855ffac533b8dc8822e01d3fee4673a"><code>d782fa1</code></a> <code>docs: Update documentation for husky 1.0 (#496)</code></li>
</ul>
<p>See the <a href="https://urls.greenkeeper.io/okonet/lint-staged/compare/d386c802b42f8e374090b1f9c58e4b60531d30ff...f82443c7f7b147aae11e65a797b280ce375c8515">full diff</a></p>
</details>

<details>
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</details>

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