ResourceRelatedField edited to work with plural names

[arthur-s]

example to use:

members = ResourceRelatedField(
        queryset=Internal.objects.all(),
        many=True,
        related_resource_name='internals'
    )

When ManyToMany relation, ResourceRelatedField expects the relation type named internal, while my app sends to server data like

members: {data: [{type: "internals", id: "1"}, {type: "internals", id: "4"}]}

Also simplified choices property

[jerel]

Thanks for this. I'm going to close it since #152 or http://django-rest-framework-json-api.readthedocs.org/en/latest/usage.html#inflecting-object-and-relation-keys should solve any pluralization issues with relationships.