v1.4.6

• Use record.ref() to get the Firebase reference for a particular record, including embedded records.
• Embedded records, when calling .save() directly, will no longer write data at the root collection level in the db.
• Embedded records, when calling .destroyRecord() directly, will correctly be removed on the server.
• Embedded belongsTo records correctly serialize an id.
• Embedded records clear their isDirty and isNew state when saving directly or via the parent, fixing record.rollback().
• Use modelName instead of typeKey to get rid of Ember Data beta.18 deprecation warnings.