Add serialization_scope and default_serializer_options

Added in serialization_scope and default_serializer_options. Right now this is just a like for like addition from 0.8 but this should open up the ability for adapter to modify this. 

For example the JsonApi adapter will probably want the default_serializer_options to include the values of the page, sort, include and fields parameters. The adapter could define this list and we would use the currently configured adapter to define what the default serializer_options are.

Thoughts?
When Rails serializes json it passes options to as_json method. This is why we may want to pass options to adapter.
From the other hand most of options tells as what to serialize, not how. This is the reason to pass options to serializer.

I think end user may pass serializer option and adapter options in one plase. E.g.

    render json: @collection, each_serializer: AssetSerializer, root: 'assets'

So we may separate serializer options from adapter options. I'll try to implement that in couple of days.