Change Modulefile to metadata.json because Modulefile is deprecated

Modulefile

-name 'gentoo-portage'
-version '2.2.0'
-license 'GPLv2'
-summary 'Puppet types and providers for Gentoo portage'
-project_page 'https://github.com/gentoo/puppet-portage'
-
-dependency 'puppetlabs/concat', '1.x'

metadata.json

+{
+  "name": "gentoo-portage",
+  "version": "2.2.0",
+  "author": "Gentoo",
+  "summary": "Puppet types and providers for Gentoo portage",
+  "license": "GPLv2",
+  "source": "https://github.com/gentoo/puppet-portage.git",
+  "project_page": "https://github.com/gentoo/puppet-portage",
+  "issues_url": "https://github.com/gentoo/puppet-portage/issues",
+  "dependencies": [
+    {
+      "name": "puppetlabs/concat",
+      "version_range": ">= 1.0.2"
+    }
+  ]
+}