metadata: added ubuntu, centos and debian support

metadata.rb

@@ -5,3 +5,8 @@ license          'Apache 2.0'
 description      'Installs/Configures dovecot'
 long_description IO.read(File.join(File.dirname(__FILE__), 'README.md'))
 version          '0.1.0'
+
+supports 'centos'
+supports 'debian'
+supports 'ubuntu'
+