Allows providing a `module_namespace` option

This is passed through to the active record object, so that it can prepend the module namespace to the serializer name before constantizing it.

[x] Allows easy versioning for serializers
If you want to version your serializers, your controller can now do so easily.

[x] Allows creating a more controller/view pattern

application_controller.rb
```ruby
  def default_serializer_options
    {module_namespace: self.class.name.deconstantize}
  end
```

path structure
```
|- controllers
|  |- api
|     |- v1
|         posts_controller.rb
|- serializers
   |- api
      |- v1
          posts_serializer.rb
```