Auto merge of #5900 - ember-cli:greenkeeper-npm-2.15.5, r=rwjblue
Auto merge of #5900 - ember-cli:greenkeeper-npm-2.15.5, r=rwjblue

Update npm to version 2.15.5 🚀

Hello :wave:

:rocket::rocket::rocket:

[npm](https://www.npmjs.com/package/npm) just published its new version 2.15.5, which **is not covered by your current version range**.

If this pull request passes your tests you can publish your software with the latest version of npm – otherwise use this branch to work on adaptions and fixes.

Happy fixing and merging :palm_tree:

---
[GitHub Release](https://github.com/npm/npm/releases/tag/v2.15.5)

<h3>v2.15.5 (2016-05-05):</h3>

<p>This is a minor LTS release, bringing dependencies up to date and updating our CI matrix to match what we support.</p>

<p>Some of the dependency updates come out of our getting the development branch's tests passing on Windows and so bring in fixes for a few Windows related corner cases.</p>

<h4>CI UPDATES</h4>

<ul>
<li>
<a href="http://urls.greenkeeper.io/npm/npm/commit/bb6f0e5c95d4ad186768b1c962dd4c399f90ddb1"><code>bb6f0e5</code></a> <a href="http://urls.greenkeeper.io/npm/npm/pull/12487">#12487</a> Remove iojs from CI, add Node.js 6, prioritize 4 over 5. (<a href="http://urls.greenkeeper.io/othiym23">@othiym23</a>)</li>
</ul>

<h4>DEPENDENCY UPDATES</h4>

<ul>
<li>
<a href="http://urls.greenkeeper.io/npm/npm/commit/f2f8753c4aef2a604a4bdca2677711c940234b8f"><code>f2f8753</code></a> <code>which@1.2.8</code>: Properly handle relative path executables. (<a href="http://urls.greenkeeper.io/isaacs">@isaacs</a>)</li>
<li>
<a href="http://urls.greenkeeper.io/npm/npm/commit/e287ca99c37680d8e4cfacf4cfebe2da98884865"><code>e287ca9</code></a> <code>read-package-json@2.0.4</code>: Fix Windows issue with ENOTDIR detection. (<a href="http://urls.greenkeeper.io/zkat">@zkat</a>)</li>
<li>
<a href="http://urls.greenkeeper.io/npm/npm/commit/1a0ce6cff4c347bad035dc89bba2ceed9dacbf73"><code>1a0ce6c</code></a> <code>realize-package-specifier@3.0.3</code>: Use npa with windows fix. Fix relative path resolution when the local file might also be a tag. (<a href="http://urls.greenkeeper.io/zkat">@zkat</a>) (<a href="http://urls.greenkeeper.io/iarna">@iarna</a>)</li>
<li>
<a href="http://urls.greenkeeper.io/npm/npm/commit/a475c9a4e4b36d00080b11f379657ce68185adc6"><code>a475c9a</code></a> <code>lru-cache@4.0.1</code>: Use Symbol if available. (<a href="http://urls.greenkeeper.io/isaacs">@isaacs</a>)</li>
<li>
<a href="http://urls.greenkeeper.io/npm/npm/commit/7141e08816c620b1889d7537c30dc5b254de4d1f"><code>7141e08</code></a> <code>sorted-object@2.0.0</code> (<a href="http://urls.greenkeeper.io/iamstarkov">@iamstarkov</a>)</li>
<li>
<a href="http://urls.greenkeeper.io/npm/npm/commit/27c6190216cc8a5a280f0efbabb3444581968d40"><code>27c6190</code></a> <code>request@2.72.0</code> (<a href="http://urls.greenkeeper.io/simov">@simov</a>)</li>
<li>
<a href="http://urls.greenkeeper.io/npm/npm/commit/ab90daf70ba51b51f722fb4cd74ac5267621c4b4"><code>ab90daf</code></a> <code>readable-stream@2.1.2</code> (<a href="http://urls.greenkeeper.io/calvinmetcalf">@calvinmetcalf</a>)</li>
<li>
<a href="http://urls.greenkeeper.io/npm/npm/commit/b1715f805426403273225bcfa91d1a52d7b56eb8"><code>b1715f8</code></a> <code>graceful-fs@4.1.4</code> (<a href="http://urls.greenkeeper.io/isaacs">@isaacs</a>)</li>
<li>
<a href="http://urls.greenkeeper.io/npm/npm/commit/ca97de6c18059ef420235f4706898ad8758904e6"><code>ca97de6</code></a> <code>block-stream@0.0.9</code> (<a href="http://urls.greenkeeper.io/isaacs">@isaacs</a>)</li>
</ul>

---
The new version differs by 46 commits .

- [`de55f5b`](https://github.com/npm/npm/commit/de55f5bb0b1c3cf6716dd855181d774787475171) `2.15.5`
- [`650cf10`](https://github.com/npm/npm/commit/650cf10848ad2ae7af15f11badbda30cb3718af3) `doc: changelog for 2.15.5`
- [`c276c07`](https://github.com/npm/npm/commit/c276c079dead72394a4761b0584f17c960145932) `sprintf-js@1.0.3`
- [`5820574`](https://github.com/npm/npm/commit/5820574fdf0731815ee1ce0ea8dbd4532a7b68bf) `require-inject@1.3.1`
- [`e7f2f7d`](https://github.com/npm/npm/commit/e7f2f7d500fe23408c10e2148ebc30bb7815f245) `npm-registry-mock@1.0.1`
- [`9191cf9`](https://github.com/npm/npm/commit/9191cf99c342d054a09171cdf6268788337e7b03) `tacks@1.2.1`
- [`3c3556a`](https://github.com/npm/npm/commit/3c3556add09233e81467c635c57e2ac3bf280ce6) `tap@5.7.1`
- [`f2f8753`](https://github.com/npm/npm/commit/f2f8753c4aef2a604a4bdca2677711c940234b8f) `which@1.2.8`
- [`7141e08`](https://github.com/npm/npm/commit/7141e08816c620b1889d7537c30dc5b254de4d1f) `sorted-object@2.0.0`
- [`27c6190`](https://github.com/npm/npm/commit/27c6190216cc8a5a280f0efbabb3444581968d40) `request@2.72.0`
- [`1a0ce6c`](https://github.com/npm/npm/commit/1a0ce6cff4c347bad035dc89bba2ceed9dacbf73) `realize-package-specifier@3.0.3`
- [`598c3a1`](https://github.com/npm/npm/commit/598c3a17d49daaddeab7d1400ccb881560e7432c) `dedupe: npmlog had unnecessary duplicates in it`
- [`ab90daf`](https://github.com/npm/npm/commit/ab90daf70ba51b51f722fb4cd74ac5267621c4b4) `readable-stream@2.1.2`
- [`e287ca9`](https://github.com/npm/npm/commit/e287ca99c37680d8e4cfacf4cfebe2da98884865) `read-package-json@2.0.4`
- [`a475c9a`](https://github.com/npm/npm/commit/a475c9a4e4b36d00080b11f379657ce68185adc6) `lru-cache@4.0.1`

There are 46 commits in total. See the [full diff](https://github.com/npm/npm/compare/e93d20877150a78c5147031866a550d256f46529...de55f5bb0b1c3cf6716dd855181d774787475171).

---
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