Merge #3809

3809: Update commitizen to the latest version 🚀 r=jniles a=greenkeeper[bot]


## The devDependency [commitizen](https://github.com/commitizen/cz-cli) was updated from `3.1.2` to `4.0.0`.
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.

---

**Publisher:** [commitizen-bot](https://www.npmjs.com/~commitizen-bot)
**License:** MIT

<details>
<summary>Release Notes for v4.0.0</summary>

<h1><a href="https://urls.greenkeeper.io/commitizen/cz-cli/compare/v3.1.2...v4.0.0">4.0.0</a> (2019-07-18)</h1>
<h3>Bug Fixes</h3>
<ul>
<li><strong>node:</strong> remove node 6 and 8 support (<a href="https://urls.greenkeeper.io/commitizen/cz-cli/issues/649" data-hovercard-type="pull_request" data-hovercard-url="/commitizen/cz-cli/pull/649/hovercard">#649</a>) (<a href="https://urls.greenkeeper.io/commitizen/cz-cli/commit/8931c6b">8931c6b</a>)</li>
</ul>
<h3>BREAKING CHANGES</h3>
<ul>
<li><strong>node:</strong> Removal of two major node versions, 6 and 8 from testing scheme</li>
</ul>
</details>

<details>
<summary>Commits</summary>
<p>The new version differs by 2 commits.</p>
<ul>
<li><a href="https://urls.greenkeeper.io/commitizen/cz-cli/commit/8931c6b9882ad83e07a21800c9caf42454d80952"><code>8931c6b</code></a> <code>fix(node): remove node 6 and 8 support (#649)</code></li>
<li><a href="https://urls.greenkeeper.io/commitizen/cz-cli/commit/ad6f14c6f40f879e2775f12b19a155ed1143b5a2"><code>ad6f14c</code></a> <code>chore(deps): update dependency semantic-release to v15.13.18 (#644)</code></li>
</ul>
<p>See the <a href="https://urls.greenkeeper.io/commitizen/cz-cli/compare/4417fcfc7f4715db48aa2e529cb112f32972d1cf...8931c6b9882ad83e07a21800c9caf42454d80952">full diff</a></p>
</details>

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<details>
  <summary>FAQ and help</summary>

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</details>

---


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package.json

@@ -112,7 +112,7 @@
     "chai-as-promised": "^7.1.1",
     "chai-datetime": "^1.5.0",
     "chai-http": "^1.0.0",
-    "commitizen": "^3.0.5",
+    "commitizen": "^4.0.0",
     "cssnano": "^4.1.10",
     "cz-conventional-changelog": "^2.1.0",
     "del": "^5.0.0",