Auto merge of #1705 - MarkMT:retrieving_related_records, r=locks
Auto merge of #1705 - MarkMT:retrieving_related_records, r=locks

Explain retrieval of related records

This commit adds a sub-section to Models: Relationships to explain how to retrieve records from related models using the JSON API 'include' query parameter. This reflects recent changes to the `DS.Store` API documented in https://github.com/emberjs/data/pull/4581

jkarsrud/guides,knownasilya/guides,MarkMT/guides,knownasilya/guides,nicobot/guides,nicobot/guides,knownasilya/guides,davidpett/guides,knownasilya/guides,jkarsrud/guides,HeroicEric/guides,skaterdav85/guides,MarkMT/guides,HeroicEric/guides,MarkMT/guides,davidpett/guides,tleskin/guides,skaterdav85/guides,tleskin/guides,nicobot/guides,MarkMT/guides,skaterdav85/guides,jkarsrud/guides,skaterdav85/guides,HeroicEric/guides,jkarsrud/guides,davidpett/guides,tleskin/guides,davidpett/guides