Bring back 'amazon' package family

Chef docs claim they are included into 'rhel' but apparently
that's not the case according to Kitchen tests?

providers/erlang_package_from_bintray.rb

@@ -62,7 +62,7 @@ action :install do
     end
   end
 
-  if platform_family?('rhel', 'fedora')
+  if platform_family?('rhel', 'fedora', 'amazon')
     package new_resource.name do
       package_name 'erlang'
       version new_resource.version unless new_resource.version.nil?

recipes/erlang_package.rb

@@ -55,7 +55,7 @@ if platform_family?('rhel')
   end
 end
 
-if platform_family?('rhel', 'fedora')
+if platform_family?('rhel', 'fedora', 'amazon')
   rabbitmq_erlang_yum_repository_on_bintray 'rabbitmq_erlang' do
     baseurl node['rabbitmq']['erlang']['yum']['baseurl']
     gpgkey node['rabbitmq']['erlang']['yum']['gpgkey']