Fix active_model_serializer link

Repo was moved to rails-api organization
Fix typo in store error message
Merge pull request #631 from bobbus/fix-store-error-typo

Fix typo in store.findMany error message
Merge pull request #627 from strzalek/patch-1

Fix active_model_serializer link
Extract embedded `belongsTo` records properly

`sideload` won't consider relationships/embedded records, by using
`extractRecordRepresentation` we'll recurse into the record (similarly
to `extractEmbeddedHasMany`).
Merge pull request #637 from sandstrom/extract-embedded-belongs-to

Extract embedded `belongsTo` records properly
Use of references instead of clientId