Fix #1759, Grape integration, adds serialization_context (#4)

* Fix #1759, Grape integration, adds serialization_context

- `serialization_context` is added in grape formatter so grape continues to render models without an explicit call to the `render` helper method
- Made it straightforward for subclasses to add other serializer options (such as `serialization_scope`).

* Updated Grape tests to include:
- paginated collections
- implicit Grape serializer (i.e. without explicit invocation of `render` helper method)

* Update Changelog with fixes.

lib/grape/helpers/active_model_serializers.rb

@@ -1,7 +1,5 @@
 # Helpers can be included in your Grape endpoint as: helpers Grape::Helpers::ActiveModelSerializers
 
-require 'active_model_serializers/serialization_context'
-
 module Grape
   module Helpers
     module ActiveModelSerializers
@@ -11,12 +9,6 @@ module Grape
       #
       # Example: To include pagination meta data: render(posts, meta: { page: posts.page, total_pages: posts.total_pages })
       def render(resource, active_model_serializer_options = {})
-        active_model_serializer_options.fetch(:serialization_context) do
-          active_model_serializer_options[:serialization_context] = ::ActiveModelSerializers::SerializationContext.new(
-            original_url: request.url[/\A[^?]+/],
-            query_parameters: request.params
-          )
-        end
         env[:active_model_serializer_options] = active_model_serializer_options
         resource
       end