chore(deps): bump serde from 1.0.177 to 1.0.180 (#386)

Bumps [serde](https://github.com/serde-rs/serde) from 1.0.177 to
1.0.180.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/serde-rs/serde/releases">serde's
releases</a>.</em></p>
<blockquote>
<h2>v1.0.180</h2>
<ul>
<li>Update to 2018 edition</li>
</ul>
<h2>v1.0.179</h2>
<ul>
<li>Support serialization of tuple variants inside a flattened field (<a
href="https://redirect.github.com/serde-rs/serde/issues/2448">#2448</a>,
thanks <a
href="https://github.com/Mingun"><code>@​Mingun</code></a>)</li>
</ul>
<h2>v1.0.178</h2>
<ul>
<li>Fix build error when using serde with &quot;std&quot; feature turned
off and &quot;unstable&quot; feature turned on (<a
href="https://redirect.github.com/serde-rs/serde/issues/2541">#2541</a>)</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/serde-rs/serde/commit/033d05f70b539226818403422295e16cf15bb3c4"><code>033d05f</code></a>
Release 1.0.180</li>
<li><a
href="https://github.com/serde-rs/serde/commit/fe4e3fd3b0d59e8e2bfed071b234dbae5fd779c1"><code>fe4e3fd</code></a>
Merge pull request <a
href="https://redirect.github.com/serde-rs/serde/issues/2547">#2547</a>
from dtolnay/tombstone</li>
<li><a
href="https://github.com/serde-rs/serde/commit/8a8a8a70ee8f32339623d77d44af53a39951ddd9"><code>8a8a8a7</code></a>
Delete tombstones of the __private module</li>
<li><a
href="https://github.com/serde-rs/serde/commit/339dca828dcece3a8e2d928a65ceceb5664efc6a"><code>339dca8</code></a>
Merge pull request <a
href="https://redirect.github.com/serde-rs/serde/issues/2546">#2546</a>
from dtolnay/edition</li>
<li><a
href="https://github.com/serde-rs/serde/commit/0d7349fa4e1f5edf55da03a284c856056f335b60"><code>0d7349f</code></a>
Resolve ambiguous core import on rustc 1.64 through 1.71</li>
<li><a
href="https://github.com/serde-rs/serde/commit/830528d5b109fc1e8a0c4cbe720d88e881b12088"><code>830528d</code></a>
Update to 2018 edition</li>
<li><a
href="https://github.com/serde-rs/serde/commit/ab90fbc7c982234788f64fc3d89c5d59c58ab767"><code>ab90fbc</code></a>
Apply 'cargo fix --edition'</li>
<li><a
href="https://github.com/serde-rs/serde/commit/3eec111e8f8c1a17db55d55f3aeb52a6a9be53de"><code>3eec111</code></a>
Delete support for compilers without crate::-based module system</li>
<li><a
href="https://github.com/serde-rs/serde/commit/93884336421a07c9d7f32881ee8f78228d31b066"><code>9388433</code></a>
Rename 'try!' macro to 'tri!' in preparation for 2018 edition</li>
<li><a
href="https://github.com/serde-rs/serde/commit/ba120706652cd71684e04cb1e1d9589c964d248d"><code>ba12070</code></a>
Merge pull request <a
href="https://redirect.github.com/serde-rs/serde/issues/2545">#2545</a>
from dtolnay/up</li>
<li>Additional commits viewable in <a
href="https://github.com/serde-rs/serde/compare/v1.0.177...v1.0.180">compare
view</a></li>
</ul>
</details>
<br />


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