Bump composer/installers from 1.5.0 to 1.6.0

Bumps [composer/installers](https://github.com/composer/installers) from 1.5.0 to 1.6.0.
- [Release notes](https://github.com/composer/installers/releases)
- [Changelog](https://github.com/composer/installers/blob/master/CHANGELOG.md)
- [Commits](https://github.com/composer/installers/compare/v1.5.0...v1.6.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

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",