Bump composer/installers from 1.5.0 to 1.6.0 (#137)

Bumps [composer/installers](https://github.com/composer/installers) from 1.5.0 to 1.6.0.
<details>
<summary>Changelog</summary>

*Sourced from [composer/installers's changelog](https://github.com/composer/installers/blob/master/CHANGELOG.md).*

> # Change Log
> 
> ## [Unreleased]
</details>
<details>
<summary>Commits</summary>

- [`cfcca6b`](cfcca6b1b6) Merge pull request [#397](https://github-redirect.dependabot.com/composer/installers/issues/397) from harmenjanssen/normalize-october-plugin
- [`8da283a`](8da283adf7) Normalise vendor directory containing hyphen
- [`5d15e4e`](5d15e4e9aa) Merge pull request [#376](https://github-redirect.dependabot.com/composer/installers/issues/376) from thomscode/disable-installers
- [`78eb8ca`](78eb8ca263) Add use statements in place of fully qualified namespaces
- [`4bff163`](4bff1637ea) Merge branch 'master' into disable-installers
- [`a118c5b`](a118c5bbb5) Merge pull request [#391](https://github-redirect.dependabot.com/composer/installers/issues/391) from davidbarratt/mediawiki-core
- [`2353998`](2353998d5a) Add MediaWiki Core
- [`c3c5297`](c3c5297a3b) Add false as an option to prevent installers from being disabled.
- [`3806135`](38061358f2) Update documentation to include false option
- [`1aa22c1`](1aa22c1756) Merge branch 'master' into disable-installers
- Additional commits viewable in [compare view](https://github.com/composer/installers/compare/v1.5.0...v1.6.0)
</details>
<br />

[![Dependabot compatibility score](https://api.dependabot.com/badges/compatibility_score?dependency-name=composer/installers&package-manager=composer&previous-version=1.5.0&new-version=1.6.0)](https://dependabot.com/compatibility-score.html?dependency-name=composer/installers&package-manager=composer&previous-version=1.5.0&new-version=1.6.0)

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---

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<details>
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</details>

composer.lock

@@ -8,16 +8,16 @@
     "packages": [
         {
             "name": "composer/installers",
-            "version": "v1.5.0",
+            "version": "v1.6.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/composer/installers.git",
-                "reference": "049797d727261bf27f2690430d935067710049c2"
+                "reference": "cfcca6b1b60bc4974324efb5783c13dca6932b5b"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/composer/installers/zipball/049797d727261bf27f2690430d935067710049c2",
-                "reference": "049797d727261bf27f2690430d935067710049c2",
+                "url": "https://api.github.com/repos/composer/installers/zipball/cfcca6b1b60bc4974324efb5783c13dca6932b5b",
+                "reference": "cfcca6b1b60bc4974324efb5783c13dca6932b5b",
                 "shasum": ""
             },
             "require": {
@@ -124,7 +124,7 @@
                 "zend",
                 "zikula"
             ],
-            "time": "2017-12-29T09:13:20+00:00"
+            "time": "2018-08-27T06:10:37+00:00"
         },
         {
             "name": "pressbooks/mix",